SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

worst-group-spurious-dfr

claude-code claude-opus-4-8 ✓ resolved GOOD_SUCCESS ↑ View task
Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.
Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.
Classification , post-hoc; cannot change the reward
GOOD_SUCCESSLegitimate solve, implements the asked-for behavior; tests verify real functionality.
SubtypeLegitimate Solution
EvidenceTest output: "COMPONENT CONFORMANCE SUITE: 194/194 cases passed (all milestones pass: True)" and "FINAL METRIC: worst-group accuracy = 0.9433 >= threshold 0.86" and "REWARD = 1". The agent's framework implementation was fully correct (all 194 component checks passed). The in-sandbox training encountered OOM in the 481MB e2b sandbox, but the verifier's documented fallback mechanism re-ran training locally with 24GB memory, which produced a valid checkpoint that achieved excellent worst-group accuracy well above the 0.86 threshold.
Root causeThe agent correctly implemented the entire deep-learning framework (all component checks passed) and wrote proper training code. The in-sandbox training OOM was an environmental constraint of the small e2b sandbox, not an agent error. The verifier's fallback to local re-training is a documented, intentional mechanism for validating code when sandbox resources are insufficient.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
281 tool calls · 4 tool types · 323 steps
Agent session started, model: claude-opus-4-8 · 29 tools available · cwd: /app
I'll start by exploring the environment to understand the structure and what's already provided.

List app structure

shell
ls -la && echo "---SUBMISSION---" && ls -la submission/ && echo "---DATA---" && ls -la data/
output
total 89
drwxr-xr-x  4 user user  4096 Jun 30 22:48 .
drwxr-xr-x 21 root root  4096 Jun 30 22:47 ..
-rw-r--r--  1 user user 14914 Jun 30 22:48 PROMPT.txt
-rw-r--r--  1 user user     5 Jun 30 22:48 agent.pid
-rw-r--r--  1 user user     0 Jun 30 22:48 agent.stderr
-rw-r--r--  1 user user  4552 Jun 30 22:48 agent_trajectory.jsonl
drwxr-xr-x  2 user user    60 Jun 30 22:48 data
-rw-r--r--  1 user user     0 Jun 30 22:48 run.log
-rwxr-xr-x  1 user user 45855 Jun 30 11:01 run_checks.py
drwxr-xr-x  3 user user   128 Jun 30 22:48 submission
-rwxr-xr-x  1 user user  1318 Jun 30 11:01 test.sh
-rwxr-xr-x  1 user user   629 Jun 30 11:01 timer.sh
---SUBMISSION---
total 100
drwxr-xr-x 3 user user   128 Jun 30 22:48 .
drwxr-xr-x 4 user user  4096 Jun 30 22:48 ..
drwxr-xr-x 2 user user  4096 Jun 30 22:48 __pycache__
-rw-r--r-- 1 user user 48121 Jun 30 11:01 autograd.py
-rw-r--r-- 1 user user  1692 Jun 30 11:01 data.py
-rw-r--r-- 1 user user 23705 Jun 30 11:01 nn.py
-rw-r--r-- 1 user user 12275 Jun 30 11:01 optim.py
-rw-r--r-- 1 user user  2900 Jun 30 11:01 train.py
---DATA---
total 11108
drwxr-xr-x 2 user user      60 Jun 30 22:48 .
drwxr-xr-x 4 user user    4096 Jun 30 22:48 ..
-rw-r--r-- 1 user user 3953364 Jun 30 11:01 reweight.npz
-rw-r--r-- 1 user user 7411924 Jun 30 11:01 train.npz

Count lines in files

shell
wc -l submission/*.py run_checks.py test.sh 2>/dev/null
output
1306 submission/autograd.py
    44 submission/data.py
   543 submission/nn.py
   272 submission/optim.py
    65 submission/train.py
   937 run_checks.py
    24 test.sh
  3191 total
This is a large task. Let me read all the files carefully, starting with the autograd framework.

/app/submission/autograd.py

contents
1	"""Reverse-mode automatic differentiation over numpy arrays.
2	
3	YOU MUST IMPLEMENT EVERYTHING MARKED ``# TODO`` / ``raise NotImplementedError`` using numpy
4	ONLY. No torch/jax/tensorflow/autograd/etc. The grader's conformance suite differentiates each
5	op below with central finite differences and compares against YOUR analytic backward, so every
6	backward must be correct (a single wrong reduction / Jacobian / group-weighting fails the checks).
7	
8	A ``Tensor`` wraps one ``numpy.ndarray`` (stored as ``float64`` in ``self.data``) and records
9	the op that produced it so ``.backward()`` can accumulate ``.grad`` into every leaf.
10	
11	CONTRACT (the grader builds its own reference against this exact API):
12	* ``Tensor(data, requires_grad=False)`` -- ``self.data`` is ``float64``; ``self.grad`` is None
13	  until backward, then a same-shape ``float64`` array. requires_grad leaves accumulate grad.
14	* Every op returns a NEW Tensor whose ``requires_grad`` is the OR of its differentiable inputs,
15	  and whose ``_backward`` closure does ``input._accum(local_grad)`` (so multiple paths add up).
16	* ``t.backward(grad=None)`` -- seeds ``grad`` (all-ones for a scalar) and walks the graph in
17	  reverse topological order, calling each node's ``_backward``. Repeated backward accumulates.
18	* BROADCASTING: binary ops broadcast like numpy; the backward MUST reduce (sum) the upstream
19	  gradient back to each input's ORIGINAL shape (use the provided ``_unbroadcast`` helper).
20	* 
…[truncated 52049 chars]
Now let me read the other files.

/app/submission/nn.py

contents
1	"""Neural-network layers + models + the robustness machinery, built on YOUR autograd engine.
2	
3	Implement every ``# TODO`` forward (and the robustness-helper bodies). The parameters +
4	``named_params`` naming + the checkpoint round-trip are already wired; you compose the autograd
5	ops. The grader checks each layer's forward against its OWN reference AND finite-difference-checks
6	the gradients that flow through your autograd, so the composition must be exactly right.
7	
8	THE FINAL-METRIC MODEL is the pinned ``SmallCNN`` (a conv FEATURE EXTRACTOR + a single linear
9	CLASSIFIER). The split is what makes last-layer retraining (DFR) on a group-balanced set
10	expressible against the pinned graph: freeze the extractor and re-fit ONLY ``classifier``.
11	``featurize(X, training)`` returns the post-ReLU embedding so you can freeze the extractor.
12	
13	The other layers/models (Linear / Conv2d / BatchNorm2d / BatchNorm1d / LayerNorm / Dropout /
14	AvgPool2d / MLP / ResidualMLP / a TinyConvNet) are exercised by the conformance suite across a
15	WIDE surface -- each is an independent potential bug. The robustness machinery (``GroupDROState``
16	exponentiated-gradient adversary-weight update, ``balanced_group_weights``,
17	``class_balanced_weights``, ``log_class_prior``) is the domain-specific heart this task adds; the
18	``robust`` milestone checks them.
19	
20	SmallCNN naming contract (do not change -- the verifier indexes by these exact keys):
21	  conv1.weight (Wd,3,3,3) | con
…[truncated 24273 chars]
Now optim.py, data.py, train.py:

/app/submission/optim.py

contents
1	"""Optimizers + LR schedulers + grad clipping over a flat list of autograd ``Tensor`` parameters.
2	
3	Implement the ``# TODO`` update math. All optimizers operate IN PLACE on ``param.data`` using
4	``param.grad``. ``zero_grad()`` resets every grad to None. ``t`` is the 1-based step count. The
5	grader runs one (and several) steps of each and compares your updated params against its
6	reference within a tight tolerance, so the math must be EXACTLY right -- every optimizer /
7	scheduler / clipper is an independent potential bug.
8	
9	The training recipe uses AdamW (decoupled weight decay) + ``clip_grad_norm`` for the ERM
10	extractor and the last-layer (DFR) retrain; the rest of the zoo is graded for parity.
11	
12	  SGD     : g = grad + wd*p; v = mu*v + g; upd = (g + mu*v) if nesterov else v; p -= lr*upd
13	  Adagrad : g = grad + wd*p; s += g^2; p -= lr*g/(sqrt(s)+eps)
14	  RMSprop : g = grad + wd*p; s = alpha*s + (1-alpha)*g^2; p -= lr*g/(sqrt(s)+eps)
15	  Adam    : g = grad + wd*p (COUPLED L2); m,v EMA; mhat=m/(1-b1^t); vhat=v/(1-b2^t);
16	            p -= lr*mhat/(sqrt(vhat)+eps)
17	  AdamW   : DECOUPLED wd; m,v EMA; p -= lr*( mhat/(sqrt(vhat)+eps) + wd*p )
18	  Adamax  : m=b1*m+(1-b1)*g; u=max(b2*u, |g|); p -= (lr/(1-b1^t))*m/(u+eps)   (infinity-norm)
19	  NAdam   : m,v EMA; mhat=m/(1-b1^t); vhat=v/(1-b2^t);
20	            mnes = b1*mhat + (1-b1)*g/(1-b1^t);  p -= lr*mnes/(sqrt(vhat)+eps)
21	  Lion    : upd = sign(b1*m + (1-b1)*g); p -= lr*(upd + wd*p); m = b2*m + (1-b2
…[truncated 11759 chars]

/app/submission/data.py

contents
1	"""Data loading + group helpers for the worst-group / spurious-correlation task.
2	
3	Implement the ``# TODO`` bodies (numpy only). The splits ship as ``.npz`` files with arrays
4	``X`` (N,3,S,S) float, ``y`` (the SHAPE class to predict) and ``g`` (the spurious background-color
5	id). A "group" is the pair ``(y, g)``; ``group_ids(y, g, n_classes) = y*n_classes + g`` flattens it
6	to a single id in ``[0, n_classes**2)``.
7	"""
8	from __future__ import annotations
9	
10	from typing import Dict, Tuple
11	
12	import numpy as np
13	
14	
15	def load_npz(path: str) -> Tuple[np.ndarray, np.ndarray, np.ndarray]:
16	    """Load (X, y, g) from a .npz; return float64 X, int64 y, int64 g. (Provided.)"""
17	    d = np.load(path)
18	    return (np.asarray(d["X"], dtype=np.float64),
19	            np.asarray(d["y"], dtype=np.int64),
20	            np.asarray(d["g"], dtype=np.int64))
21	
22	
23	def group_ids(y: np.ndarray, g: np.ndarray, n_classes: int) -> np.ndarray:
24	    """Flatten (y, g) to a single group id y*n_classes + g (int64)."""
25	    # TODO
26	    raise NotImplementedError("group_ids")
27	
28	
29	def iterate(X, y, g, batch_size, rng):
30	    """Yield (Xb, yb, gb) minibatches over a random permutation of the dataset."""
31	    # TODO
32	    raise NotImplementedError("iterate")
33	
34	
35	def worst_group_acc(preds, y, g, n_classes) -> Tuple[float, float, Dict[int, float]]:
36	    """Return (min over (y,g) groups of within-group accuracy, average accuracy, per-group dict)."""
37	
…[truncated 318 chars]

/app/submission/train.py

contents
1	"""Training entry point. Implement your worst-group-robust recipe, train the pinned SmallCNN,
2	and save the checkpoint the grader will load.
3	
4	Run it however you like (e.g. ``python3 /app/submission/train.py``). It MUST end by writing
5	``/app/submission/model.npz`` via ``save_checkpoint`` below. The grader loads that file into its
6	OWN reference SmallCNN (architecture pinned to WIDTH/EMBED_DIM below -- keep these) and evaluates
7	WORST-GROUP accuracy on a SEALED, group-balanced test set; you pass the metric part iff
8	worst-group accuracy >= the frozen threshold. (You ALSO must pass the component conformance suite
9	over autograd.py / nn.py / optim.py.)
10	
11	A naive cross-entropy ("ERM") run on the correlated train split will reach high AVERAGE accuracy
12	but ~0 worst-group accuracy -- it keys on the spurious background color. Removing that reliance is
13	the task. One well-known cheap recipe: train the feature extractor on the correlated data, then
14	RE-FIT ONLY the final ``classifier`` on the GROUP-BALANCED reweight split with a group-balanced
15	(group-weighted) loss so the head stops keying off color. You are free to use any method, as long
16	as you submit a state_dict for the pinned architecture.
17	"""
18	from __future__ import annotations
19	
20	import argparse
21	import json
22	import os
23	import sys
24	
25	import numpy as np
26	
27	sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
28	sys.path.insert(0, "/app")
29	sys.path.insert(0, "/app/su
…[truncated 1589 chars]
Let me look at the run_checks.py to understand exactly what's being tested and the tolerances.

/app/run_checks.py

contents
1	#!/usr/bin/env python3
2	"""PUBLIC component check runner for the from-scratch numpy framework (worst-group / spurious-
3	correlation task).
4	
5	Run this AS OFTEN AS YOU LIKE while you implement to get a per-check progress signal:
6	
7	    python3 /app/run_checks.py                      # check the framework in /app/submission
8	    python3 /app/run_checks.py --submission /dir
9	    python3 /app/run_checks.py --only robust        # focus a single milestone
10	
11	It imports YOUR modules from /app/submission (autograd.py / nn.py / optim.py / data.py), exactly
12	as the grader does, and runs a PUBLIC portion of the component conformance suite, printing a clear
13	per-check report. Each FAIL line names the exact op / layer / optimizer / robustness-loss that is
14	wrong.
15	
16	HOW THIS RELATES TO YOUR GRADE
17	------------------------------
18	This runner is a DEBUGGING AID, not the grader. It checks your framework against self-consistent
19	references it computes on its own:
20	  * autograd_grads : central FINITE-DIFFERENCE of YOUR forward vs YOUR analytic backward.
21	  * nn_forward     : mathematical PROPERTIES your forward must satisfy.
22	  * optim          : YOUR optimizer step vs the closed-form update re-derived here in numpy, for
23	                     every optimizer + the LR schedulers + both grad clippers.
24	  * robust         : finite-diff of YOUR robustness-loss backward + the per-group-normalization /
25	                     Group-DRO / weight-helper PROPERTI
…[truncated 47999 chars]
This is a large but mechanical task. Let me set up tracking and verify the environment first.

Inspect test.sh and data

shell
cat test.sh && echo "---" && python3 -c "import numpy; print(numpy.__version__)" && python3 -c "import numpy as np; d=np.load('data/train.npz'); print({k:(v.shape,v.dtype) for k,v in d.items()}); print('y vals',np.unique(d['y']),'g vals',np.unique(d['g'])); import collections; print('counts', collections.Counter(zip(d['y'].tolist(),d['g'].tolist())))" 2>&1 | head -40
output
#!/usr/bin/env bash
# Smoke test (NOT the grader): confirms the environment is wired -- numpy imports, the train +
# reweight splits load, and the submission stubs are present. It does NOT check correctness (the
# stubs raise NotImplementedError until you implement them).
set -uo pipefail

python3 - <<'PY'
import numpy as np, os
for f in ("train.npz", "reweight.npz"):
    assert os.path.exists(f"/app/data/{f}"), f"missing /app/data/{f}"
d = np.load("/app/data/train.npz"); r = np.load("/app/data/reweight.npz")
print(f"train X {d['X'].shape} y {d['y'].shape} g {d['g'].shape}; reweight X {r['X'].shape}")
assert r["X"].shape[1:] == d["X"].shape[1:], (r["X"].shape, d["X"].shape)
for f in ("autograd.py", "nn.py", "optim.py", "data.py", "train.py"):
    assert os.path.exists(f"/app/submission/{f}"), f"missing /app/submission/{f}"
assert os.path.exists("/app/run_checks.py"), "missing /app/run_checks.py"
print("submission stubs present:", sorted(os.listdir("/app/submission")))
print("numpy", np.__version__)
PY

# The visible check runner is present + runnable (it exits 1 on the unfilled stub, which is
# expected -- the stubs raise NotImplementedError until you implement them).
python3 /app/run_checks.py --quiet || true
echo "app_test smoke OK (run 'python3 /app/run_checks.py' to test your implementation)"
---
2.2.6
{'X': ((2400, 3, 16, 16), dtype('float32')), 'y': ((2400,), dtype('int64')), 'g': ((2400,), dtype('int64'))}
y vals [0 1 2 3] g vals [0 1 2 3]
counts Counter({(2, 2): 586, 
…[truncated 173 chars]

Inspect reweight data

shell
python3 -c "import numpy as np, collections; d=np.load('data/reweight.npz'); print({k:v.shape for k,v in d.items()}); print('counts',sorted(collections.Counter(zip(d['y'].tolist(),d['g'].tolist())).items()))"
output
{'X': (1280, 3, 16, 16), 'y': (1280,), 'g': (1280,)}
counts [((0, 0), 80), ((0, 1), 80), ((0, 2), 80), ((0, 3), 80), ((1, 0), 80), ((1, 1), 80), ((1, 2), 80), ((1, 3), 80), ((2, 0), 80), ((2, 1), 80), ((2, 2), 80), ((2, 3), 80), ((3, 0), 80), ((3, 1), 80), ((3, 2), 80), ((3, 3), 80)]
Now I understand the task fully. Let me implement `autograd.py`. First the `backward` method and an `_expand` helper.

/app/submission/autograd.py

− removed
class Tensor:
    __slots__ = ("data", "grad", "requires_grad", "_backward", "_parents")
+ added
def _expand(g: np.ndarray, in_shape: tuple, axis, keepdims: bool) -> np.ndarray:
    """Broadcast a reduced gradient ``g`` back to ``in_shape`` (inverse of a sum/mean reduction)."""
    g = _as_f64(g)
    if axis is None:
        return np.ones(in_shape, dtype=np.float64) * g
    axes = (axis,) if isinstance(axis, int) else tuple(axis)
    axes = tuple(ax % len(in_shape) for ax in axes)
    if not keepdims:
        shp = list(in_shape)
        for ax in axes:
            shp[ax] = 1
        g = g.reshape(shp)
    return np.ones(in_shape, dtype=np.float64) * g


class Tensor:
    __slots__ = ("data", "grad", "requires_grad", "_backward", "_parents")

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("Tensor.backward")
+ added
        topo: List["Tensor"] = []
        visited = set()
        stack = [(self, False)]
        while stack:
            node, processed = stack.pop()
            if processed:
                topo.append(node)
                continue
            if id(node) in visited:
                continue
            visited.add(id(node))
            stack.append((node, True))
            for p in node._parents:
                if id(p) not in visited:
                    stack.append((p, False))
        if grad is None:
            grad = np.ones_like(self.data)
        self._accum(_as_f64(grad))
        for node in reversed(topo):
            node._backward()

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the element-wise binary ops:

/app/submission/autograd.py

− removed
        raise NotImplementedError("add backward")  # TODO
+ added
        g = out.grad
        if a.requires_grad:
            a._accum(_unbroadcast(g, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g, b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("sub backward")  # TODO
+ added
        g = out.grad
        if a.requires_grad:
            a._accum(_unbroadcast(g, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(-g, b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("mul backward")  # TODO
+ added
        g = out.grad
        if a.requires_grad:
            a._accum(_unbroadcast(g * b.data, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * a.data, b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("div backward")  # TODO
+ added
        g = out.grad
        if a.requires_grad:
            a._accum(_unbroadcast(g / b.data, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(-g * a.data / (b.data * b.data), b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("power backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * pf * a.data ** (pf - 1.0))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("maximum backward")  # TODO
+ added
        g = out.grad
        am = (a.data > b.data).astype(np.float64)
        bm = (b.data > a.data).astype(np.float64)
        eq = (a.data == b.data).astype(np.float64) * 0.5
        if a.requires_grad:
            a._accum(_unbroadcast(g * (am + eq), a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * (bm + eq), b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("minimum backward")  # TODO
+ added
        g = out.grad
        am = (a.data < b.data).astype(np.float64)
        bm = (b.data < a.data).astype(np.float64)
        eq = (a.data == b.data).astype(np.float64) * 0.5
        if a.requires_grad:
            a._accum(_unbroadcast(g * (am + eq), a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * (bm + eq), b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("where backward")  # TODO
+ added
        g = out.grad
        cf = c.astype(np.float64)
        if a.requires_grad:
            a._accum(_unbroadcast(g * cf, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * (1.0 - cf), b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the unary math ops:

/app/submission/autograd.py

− removed
        raise NotImplementedError("exp backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * e)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("log backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad / a.data)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("sqrt backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * 0.5 / s)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("abs backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * np.sign(a.data))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("clip backward")  # TODO
+ added
        if a.requires_grad:
            mask = (a.data > lo) & (a.data < hi)
            a._accum(out.grad * mask)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now reductions/reshape:

/app/submission/autograd.py

− removed
        raise NotImplementedError("sum backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(_expand(out.grad, a.data.shape, axis, keepdims))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("mean backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(_expand(out.grad, a.data.shape, axis, keepdims) / n)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("max backward")  # TODO
+ added
        if a.requires_grad:
            mask = (a.data == m).astype(np.float64)
            counts = mask.sum(axis=axis, keepdims=True)
            gb = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(mask * gb / counts)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("min backward")  # TODO
+ added
        if a.requires_grad:
            mask = (a.data == m).astype(np.float64)
            counts = mask.sum(axis=axis, keepdims=True)
            gb = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(mask * gb / counts)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("transpose backward")  # TODO
+ added
        if a.requires_grad:
            if axes is None:
                a._accum(np.transpose(out.grad))
            else:
                inv = np.argsort(axes)
                a._accum(np.transpose(out.grad, inv))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("reshape backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad.reshape(a.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("getitem backward")  # TODO
+ added
        if a.requires_grad:
            ga = np.zeros_like(a.data)
            np.add.at(ga, idx, out.grad)
            a._accum(ga)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("concat backward")  # TODO
+ added
        g = out.grad
        start = 0
        for t, sz in zip(ts, sizes):
            sl = [slice(None)] * g.ndim
            sl[axis] = slice(start, start + sz)
            if t.requires_grad:
                t._accum(g[tuple(sl)])
            start += sz

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("stack backward")  # TODO
+ added
        g = out.grad
        for i, t in enumerate(ts):
            if t.requires_grad:
                t._accum(np.take(g, i, axis=axis))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("matmul backward")  # TODO
+ added
        g = out.grad
        if a.requires_grad:
            a._accum(_unbroadcast(g @ np.swapaxes(b.data, -1, -2), a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(np.swapaxes(a.data, -1, -2) @ g, b.data.shape))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the nonlinearities:

/app/submission/autograd.py

− removed
        raise NotImplementedError("relu backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * (a.data > 0.0))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("leaky_relu backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * np.where(a.data > 0.0, 1.0, sl))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("sigmoid backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * s * (1.0 - s))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("tanh backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * (1.0 - t * t))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("gelu backward")  # TODO
+ added
        if a.requires_grad:
            pdf = np.exp(-0.5 * x * x) / np.sqrt(2.0 * np.pi)
            a._accum(out.grad * (cdf + x * pdf))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("softmax backward")  # TODO
+ added
        if a.requires_grad:
            g = out.grad
            tmp = (g * s).sum(axis=axis, keepdims=True)
            a._accum(s * (g - tmp))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("log_softmax backward")  # TODO
+ added
        if a.requires_grad:
            g = out.grad
            a._accum(g - s * g.sum(axis=axis, keepdims=True))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now extra activations and reductions (softplus, silu, elu, mish, hardtanh, var, std, cumsum):

/app/submission/autograd.py

− removed
        raise NotImplementedError("softplus backward")  # TODO
+ added
        if a.requires_grad:
            sig = 1.0 / (1.0 + np.exp(-bx))
            a._accum(out.grad * sig)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("silu backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * (sig + a.data * sig * (1.0 - sig)))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("elu backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * np.where(x > 0.0, 1.0, al * ex))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("mish backward")  # TODO
+ added
        if a.requires_grad:
            sig = 1.0 / (1.0 + np.exp(-x))
            a._accum(out.grad * (t + x * (1.0 - t * t) * sig))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("hardtanh backward")  # TODO
+ added
        if a.requires_grad:
            mask = (a.data > lo) & (a.data < hi)
            a._accum(out.grad * mask)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("var backward")  # TODO
+ added
        if a.requires_grad:
            gb = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(gb * 2.0 * (a.data - mu) / (n - ddof))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("std backward")  # TODO
+ added
        if a.requires_grad:
            gb = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(gb * (a.data - mu) / (n * skeep))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("cumsum backward")  # TODO
+ added
        if a.requires_grad:
            g = out.grad
            gr = np.flip(np.cumsum(np.flip(g, axis=axis), axis=axis), axis=axis)
            a._accum(gr)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the losses (mse, cross_entropy, and robustness losses):

/app/submission/autograd.py

− removed
        raise NotImplementedError("mse_loss backward")  # TODO
+ added
        if pred.requires_grad:
            pred._accum(2.0 * diff / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("cross_entropy backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum((sm - y) / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("group_weighted_ce backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum((sm - y) * scale[:, None] * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("reweighted_ce backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum((sm - y) * (w / wsum)[:, None] * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("group_dro_loss backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum((sm - y) * scale[:, None] * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("logit_adjusted_ce backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum((sm - y) / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("focal_loss backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            dfl_dp = g * (1.0 - p) ** (g - 1.0) * np.log(pc) - (1.0 - p) ** g / pc
            coef = dfl_dp * p
            logits._accum(coef[:, None] * (y - sm) / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("irm_penalty backward")  # TODO
+ added
        if logits.requires_grad:
            sx = (sm * x).sum(axis=-1, keepdims=True)
            inner = (sm - y) + sm * (x - sx)
            logits._accum(2.0 * grad_w * (1.0 / n) * inner * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now gce, vrex, ldam, spectral_decoupling, and the norms + spatial ops:

/app/submission/autograd.py

− removed
        raise NotImplementedError("gce_loss backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            coef = -(pc ** qf)
            logits._accum(coef[:, None] * (y - sm) / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("vrex_penalty backward")  # TODO
+ added
        if r.requires_grad:
            r._accum((2.0 / K) * (r.data - mu) * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("ldam_loss backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum(sc * (sm - y) / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("spectral_decoupling backward")  # TODO
+ added
        if logits.requires_grad:
            logits._accum(lm * x / n * out.grad)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("layernorm backward")  # TODO
+ added
        g = out.grad
        if gamma.requires_grad:
            gamma._accum(_unbroadcast(g * xhat, gamma.data.shape))
        if beta.requires_grad:
            beta._accum(_unbroadcast(g, beta.data.shape))
        if a.requires_grad:
            gy = g * gamma.data
            mgy = gy.mean(axis=-1, keepdims=True)
            mgyx = (gy * xhat).mean(axis=-1, keepdims=True)
            a._accum(inv * (gy - mgy - xhat * mgyx))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("batchnorm backward")  # TODO
+ added
        g = out.grad
        if gamma.requires_grad:
            gamma._accum(_unbroadcast(g * xhat, gamma.data.shape))
        if beta.requires_grad:
            beta._accum(_unbroadcast(g, beta.data.shape))
        if a.requires_grad:
            gy = g * gamma.data
            mgy = gy.mean(axis=0, keepdims=True)
            mgyx = (gy * xhat).mean(axis=0, keepdims=True)
            a._accum(inv * (gy - mgy - xhat * mgyx))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("batchnorm2d backward")  # TODO
+ added
        g = out.grad
        gC = gamma.data.reshape(1, C, 1, 1)
        if gamma.requires_grad:
            gamma._accum((g * xhat).sum(axis=(0, 2, 3)))
        if beta.requires_grad:
            beta._accum(g.sum(axis=(0, 2, 3)))
        if x.requires_grad:
            gy = g * gC
            if training:
                mgy = gy.mean(axis=(0, 2, 3), keepdims=True)
                mgyx = (gy * xhat).mean(axis=(0, 2, 3), keepdims=True)
                x._accum(inv * (gy - mgy - xhat * mgyx))
            else:
                x._accum(gy * inv)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("rms_norm backward")  # TODO
+ added
        g = out.grad
        if gamma.requires_grad:
            gamma._accum(_unbroadcast(g * xhat, gamma.data.shape))
        if a.requires_grad:
            gy = g * gamma.data
            s = (gy * x).sum(axis=-1, keepdims=True)
            a._accum(r * gy - (r ** 3 / D) * x * s)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("groupnorm2d backward")  # TODO
+ added
        g = out.grad
        gC = gamma.data.reshape(1, C, 1, 1)
        if gamma.requires_grad:
            gamma._accum((g * xhat).sum(axis=(0, 2, 3)))
        if beta.requires_grad:
            beta._accum(g.sum(axis=(0, 2, 3)))
        if x.requires_grad:
            gy = (g * gC).reshape(N, G, m)
            xhg = xhat.reshape(N, G, m)
            mgy = gy.mean(axis=2, keepdims=True)
            mgyx = (gy * xhg).mean(axis=2, keepdims=True)
            dxg = inv * (gy - mgy - xhg * mgyx)
            x._accum(dxg.reshape(N, C, H, W))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the spatial conv/pool ops, embedding, dropout:

/app/submission/autograd.py

− removed
        raise NotImplementedError("conv2d backward")  # TODO
+ added
        g = out.grad.reshape(N, Cout, OH * OW)
        if weight.requires_grad:
            dWm = np.einsum("nop,nkp->ok", g, cols)
            weight._accum(dWm.reshape(Cout, Cin, kh, kw))
        if bias.requires_grad:
            bias._accum(out.grad.sum(axis=(0, 2, 3)))
        if x.requires_grad:
            dcols = np.einsum("ok,nop->nkp", Wm, g)
            dcols = dcols.reshape(N, Cin, kh, kw, OH, OW)
            H, W = x.data.shape[2], x.data.shape[3]
            Hp, Wp = H + 2 * pad, W + 2 * pad
            dxp = np.zeros((N, Cin, Hp, Wp), dtype=np.float64)
            for i in range(kh):
                for j in range(kw):
                    dxp[:, :, i:i + st * OH:st, j:j + st * OW:st] += dcols[:, :, i, j]
            dx = dxp[:, :, pad:pad + H, pad:pad + W] if pad > 0 else dxp
            x._accum(dx)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("maxpool2d backward")  # TODO
+ added
        if x.requires_grad:
            Hk, Wk = H // k, W // k
            xr2 = xd.reshape(N, C, Hk, k, Wk, k)
            m = outd.reshape(N, C, Hk, 1, Wk, 1)
            mask = (xr2 == m).astype(np.float64)
            counts = mask.sum(axis=(3, 5), keepdims=True)
            gb = out.grad.reshape(N, C, Hk, 1, Wk, 1)
            dxr = mask * gb / counts
            x._accum(dxr.reshape(N, C, H, W))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("maxpool2d_stride backward")  # TODO
+ added
        if x.requires_grad:
            m = outd.reshape(N, C, 1, 1, OH, OW)
            mask = (win == m).astype(np.float64)
            counts = mask.sum(axis=(2, 3), keepdims=True)
            gb = out.grad.reshape(N, C, 1, 1, OH, OW)
            contrib = mask * gb / counts
            dxp = np.zeros_like(xp)
            for i in range(k):
                for j in range(k):
                    dxp[:, :, i:i + st * OH:st, j:j + st * OW:st] += contrib[:, :, i, j]
            dx = dxp[:, :, pad:pad + H, pad:pad + W] if pad else dxp
            x._accum(dx)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("avgpool2d backward")  # TODO
+ added
        if x.requires_grad:
            Hk, Wk = H // k, W // k
            gb = out.grad.reshape(N, C, Hk, 1, Wk, 1) / (k * k)
            dxr = np.ones((N, C, Hk, k, Wk, k), dtype=np.float64) * gb
            x._accum(dxr.reshape(N, C, H, W))

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("global_avg_pool backward")  # TODO
+ added
        if x.requires_grad:
            gb = out.grad.reshape(N, C, 1, 1) / (H * W)
            x._accum(np.ones((N, C, H, W), dtype=np.float64) * gb)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("embedding backward")  # TODO
+ added
        if weight.requires_grad:
            gw = np.zeros_like(weight.data)
            np.add.at(gw, idx, out.grad)
            weight._accum(gw)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        def _bw_id():
            raise NotImplementedError("dropout backward")  # TODO
        out._backward = _bw_id
+ added
        def _bw_id():
            if a.requires_grad:
                a._accum(out.grad)
        out._backward = _bw_id

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/autograd.py

− removed
        raise NotImplementedError("dropout backward")  # TODO
+ added
        if a.requires_grad:
            a._accum(out.grad * keep)

contents
The file /app/submission/autograd.py has been updated successfully. (file state is current in your context , no need to Read it back)

Check remaining stubs in autograd

shell
cd /app/submission && grep -n "NotImplementedError\|# TODO" autograd.py
output
3:YOU MUST IMPLEMENT EVERYTHING MARKED ``# TODO`` / ``raise NotImplementedError`` using numpy
autograd.py is complete. Now let me implement `optim.py`:

/app/submission/optim.py

− removed
        # TODO: implement the SGD update (see module docstring). Update p.data in place.
        raise NotImplementedError("SGD.step")
+ added
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            v = self.momentum * self._v[i] + g
            self._v[i] = v
            upd = (g + self.momentum * v) if self.nesterov else v
            p.data -= self.lr * upd

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the Adagrad update (see module docstring). Update p.data in place.
        raise NotImplementedError("Adagrad.step")
+ added
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._s[i] = self._s[i] + g * g
            p.data -= self.lr * g / (np.sqrt(self._s[i]) + self.eps)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the RMSprop update (see module docstring). Update p.data in place.
        raise NotImplementedError("RMSprop.step")
+ added
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._s[i] = self.alpha * self._s[i] + (1 - self.alpha) * (g * g)
            p.data -= self.lr * g / (np.sqrt(self._s[i]) + self.eps)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the Adam update (see module docstring). Update p.data in place.
        raise NotImplementedError("Adam.step")
+ added
        self.t += 1
        t = self.t
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._m[i] = self.b1 * self._m[i] + (1 - self.b1) * g
            self._v[i] = self.b2 * self._v[i] + (1 - self.b2) * (g * g)
            mhat = self._m[i] / (1 - self.b1 ** t)
            vhat = self._v[i] / (1 - self.b2 ** t)
            p.data -= self.lr * mhat / (np.sqrt(vhat) + self.eps)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the AdamW update (see module docstring). Update p.data in place.
        raise NotImplementedError("AdamW.step")
+ added
        self.t += 1
        t = self.t
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            self._m[i] = self.b1 * self._m[i] + (1 - self.b1) * g
            self._v[i] = self.b2 * self._v[i] + (1 - self.b2) * (g * g)
            mhat = self._m[i] / (1 - self.b1 ** t)
            vhat = self._v[i] / (1 - self.b2 ** t)
            p.data -= self.lr * (mhat / (np.sqrt(vhat) + self.eps) + self.weight_decay * p.data)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the Adamax update (see module docstring). Update p.data in place.
        raise NotImplementedError("Adamax.step")
+ added
        self.t += 1
        t = self.t
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._m[i] = self.b1 * self._m[i] + (1 - self.b1) * g
            self._u[i] = np.maximum(self.b2 * self._u[i], np.abs(g))
            p.data -= (self.lr / (1 - self.b1 ** t)) * self._m[i] / (self._u[i] + self.eps)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the NAdam update (see module docstring). Update p.data in place.
        raise NotImplementedError("NAdam.step")
+ added
        self.t += 1
        t = self.t
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._m[i] = self.b1 * self._m[i] + (1 - self.b1) * g
            self._v[i] = self.b2 * self._v[i] + (1 - self.b2) * (g * g)
            mhat = self._m[i] / (1 - self.b1 ** t)
            vhat = self._v[i] / (1 - self.b2 ** t)
            mnes = self.b1 * mhat + (1 - self.b1) * g / (1 - self.b1 ** t)
            p.data -= self.lr * mnes / (np.sqrt(vhat) + self.eps)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the Lion update (see module docstring). Update p.data in place.
        raise NotImplementedError("Lion.step")
+ added
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            upd = np.sign(self.b1 * self._m[i] + (1 - self.b1) * g)
            p.data -= self.lr * (upd + self.weight_decay * p.data)
            self._m[i] = self.b2 * self._m[i] + (1 - self.b2) * g

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now RAdam, AdaBelief, clippers, and schedulers:

/app/submission/optim.py

− removed
        # TODO: implement the RAdam update (see module docstring). Update p.data in place.
        raise NotImplementedError("RAdam.step")
+ added
        self.t += 1
        t = self.t
        b1, b2, eps = self.b1, self.b2, self.eps
        bc1 = 1 - b1 ** t
        bc2 = 1 - b2 ** t
        rinf = 2 / (1 - b2) - 1
        rt = rinf - 2 * t * (b2 ** t) / bc2
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad + self.weight_decay * p.data
            self._m[i] = b1 * self._m[i] + (1 - b1) * g
            self._v[i] = b2 * self._v[i] + (1 - b2) * (g * g)
            mhat = self._m[i] / bc1
            if rt > 4:
                l = np.sqrt(bc2 / (self._v[i] + eps))
                r = math.sqrt(((rt - 4) * (rt - 2) * rinf) / ((rinf - 4) * (rinf - 2) * rt))
                p.data -= self.lr * mhat * r * l
            else:
                p.data -= self.lr * mhat

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
        # TODO: implement the AdaBelief update (see module docstring). Update p.data in place.
        raise NotImplementedError("AdaBelief.step")
+ added
        self.t += 1
        t = self.t
        b1, b2, eps = self.b1, self.b2, self.eps
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            self._m[i] = b1 * self._m[i] + (1 - b1) * g
            d = g - self._m[i]
            self._s[i] = b2 * self._s[i] + (1 - b2) * (d * d) + eps
            mhat = self._m[i] / (1 - b1 ** t)
            shat = self._s[i] / (1 - b2 ** t)
            p.data -= self.lr * (mhat / (np.sqrt(shat) + eps) + self.weight_decay * p.data)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("clip_grad_norm")
+ added
    total = 0.0
    for p in params:
        if p.grad is not None:
            total += float((p.grad ** 2).sum())
    total = math.sqrt(total)
    if total > max_norm:
        scale = max_norm / (total + 1e-6)
        for p in params:
            if p.grad is not None:
                p.grad = p.grad * scale
    return total

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("clip_grad_value")
+ added
    for p in params:
        if p.grad is not None:
            p.grad = np.clip(p.grad, -clip_value, clip_value)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the schedulers, matching the reference exactly:

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("cosine_lr")
+ added
    if warmup > 0 and step < warmup:
        return base_lr * (step + 1) / warmup
    prog = min(1.0, max(0.0, (step - warmup) / max(1, total - warmup)))
    return min_lr + 0.5 * (base_lr - min_lr) * (1 + math.cos(math.pi * prog))

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("warmup_lr")
+ added
    return base_lr * (step + 1) / warmup if step < warmup else base_lr

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("step_lr")
+ added
    return base_lr * (gamma ** (step // step_size))

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("exponential_lr")
+ added
    return base_lr * (gamma ** step)

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("polynomial_lr")
+ added
    if step >= total:
        return min_lr
    return (base_lr - min_lr) * ((1 - step / total) ** power) + min_lr

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/optim.py

− removed
    # TODO: implement (see docstring).
    raise NotImplementedError("cosine_restart_lr")
+ added
    s = step
    T_ = period
    while s >= T_:
        s -= T_
        T_ *= t_mult
    return min_lr + 0.5 * (base_lr - min_lr) * (1 + math.cos(math.pi * s / max(1, T_)))

contents
The file /app/submission/optim.py has been updated successfully. (file state is current in your context , no need to Read it back)
Let me run the optim check first since it's independent:

Run optim checks

shell
cd /app && OMP_NUM_THREADS=1 python3 run_checks.py --only optim 2>&1 | tail -30
output
[optim]  21/21
  optim/SGD_1step                            OK    (max_abs=0.0e+00)
  optim/SGD_momentum_5step                   OK    (max_abs=0.0e+00)
  optim/SGD_nesterov_5step                   OK    (max_abs=0.0e+00)
  optim/Adagrad_5step                        OK    (max_abs=0.0e+00)
  optim/RMSprop_5step                        OK    (max_abs=0.0e+00)
  optim/Adam_10step_wd                       OK    (max_abs=0.0e+00)
  optim/AdamW_10step_wd                      OK    (max_abs=0.0e+00)
  optim/Adamax_8step                         OK    (max_abs=0.0e+00)
  optim/NAdam_8step                          OK    (max_abs=0.0e+00)
  optim/Lion_8step_wd                        OK    (max_abs=0.0e+00)
  optim/RAdam_12step                         OK    (max_abs=0.0e+00)
  optim/AdaBelief_8step                      OK    (max_abs=0.0e+00)
  optim/clip_grad_norm_clips                 OK    (max_abs=0.0e+00)
  optim/clip_grad_norm_noop                  OK    (max_abs=0.0e+00)
  optim/clip_grad_value                      OK    (max_abs=0.0e+00)
  optim/sched_cosine_lr                      OK    (match)
  optim/sched_warmup_lr                      OK    (match)
  optim/sched_step_lr                        OK    (match)
  optim/sched_exponential_lr                 OK    (match)
  optim/sched_polynomial_lr                  OK    (match)
  optim/sched_cosine_restart_lr              OK    (match)

----------------------------------------------------------------------
optim 21/21
TOTAL  21/21
…[truncated 165 chars]
All optim pass. Now let me implement `nn.py`. First the core layer forwards:

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        d = {"weight": self.weight}
+ added
    def forward(self, x: Tensor) -> Tensor:
        out = ag.matmul(x, self.weight)
        if self.bias is not None:
            out = ag.add(out, self.bias)
        return out

    def named_params(self):
        d = {"weight": self.weight}

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {"weight": self.weight, "bias": self.bias}
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.conv2d(x, self.weight, self.bias, pad=self.pad, stride=1)

    def named_params(self):
        return {"weight": self.weight, "bias": self.bias}

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor, training: bool = True) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}

    def buffers(self):
+ added
    def forward(self, x: Tensor, training: bool = True) -> Tensor:
        return ag.batchnorm2d(x, self.gamma, self.beta, self.running_mean, self.running_var,
                              training=training, momentum=self.momentum, eps=self.eps)

    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}

    def buffers(self):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}


class LayerNorm(Module):
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.batchnorm(x, self.gamma, self.beta, eps=self.eps)

    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}


class LayerNorm(Module):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}


class Dropout(Module):
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.layernorm(x, self.gamma, self.beta, eps=self.eps)

    def named_params(self):
        return {"gamma": self.gamma, "beta": self.beta}


class Dropout(Module):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor, training: bool = False, rng=None) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
+ added
    def forward(self, x: Tensor, training: bool = False, rng=None) -> Tensor:
        return ag.dropout(x, self.p, training, rng)

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {}


class MaxPool2d(Module):
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.avgpool2d(x, self.k)

    def named_params(self):
        return {}


class MaxPool2d(Module):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self):
        return {}


class RMSNorm(Module):
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.maxpool2d(x, self.k)

    def named_params(self):
        return {}


class RMSNorm(Module):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.rms_norm). See the docstring/contract.
        raise NotImplementedError("forward")
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.rms_norm(x, self.gamma, eps=self.eps)

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x: Tensor) -> Tensor:
        # TODO: implement (compose ag.groupnorm2d). See the docstring/contract.
        raise NotImplementedError("forward")
+ added
    def forward(self, x: Tensor) -> Tensor:
        return ag.groupnorm2d(x, self.gamma, self.beta, self.num_groups, eps=self.eps)

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the model forwards. Let me implement ResidualConvNet, SmallCNN, MLP, ResidualMLP, TinyConvNet:

/app/submission/nn.py

− removed
    def forward(self, X, training: bool = True) -> Tensor:
        # TODO: implement (stem->gn0->silu; then 2 residual blocks
        #   r=h; h=silu(b*n1(b*c1(h))); h=b*n2(b*c2(h)); h=silu(h + r);
        #   then strided downsample via ag.conv2d(h, down.weight, down.bias, pad=1, stride=2) + silu;
        #   then global-avg-pool over axes (2,3); then the linear head). Compose ag.* ops.
        raise NotImplementedError("forward")
+ added
    def forward(self, X, training: bool = True) -> Tensor:
        h = ag.silu(self.gn0(self.stem(X)))
        # block 1
        r = h
        h = ag.silu(self.b1n1(self.b1c1(h)))
        h = self.b1n2(self.b1c2(h))
        h = ag.silu(ag.add(h, r))
        # block 2
        r = h
        h = ag.silu(self.b2n1(self.b2c1(h)))
        h = self.b2n2(self.b2c2(h))
        h = ag.silu(ag.add(h, r))
        # strided downsample
        h = ag.conv2d(h, self.down.weight, self.down.bias, pad=1, stride=2)
        h = ag.silu(h)
        h = ag.global_avg_pool(h)
        return self.head(h)

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def featurize(self, X, training: bool = True) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("featurize")
    def forward(self, X, training: bool = True) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
+ added
    def featurize(self, X, training: bool = True) -> Tensor:
        h = ag.relu(self.bn1(self.conv1(X), training=training))
        h = ag.maxpool2d(h, 2)
        h = ag.relu(self.bn2(self.conv2(h), training=training))
        h = ag.maxpool2d(h, 2)
        h = ag.relu(self.bn3(self.conv3(h), training=training))
        h = ag.global_avg_pool(h)
        h = ag.relu(self.embed(h))
        return h

    def forward(self, X, training: bool = True) -> Tensor:
        feat = self.featurize(X, training=training)
        return self.classifier(feat)

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for i, lin in enumerate(self.layers):
+ added
    def forward(self, x) -> Tensor:
        h = x
        n = len(self.layers)
        for i, lin in enumerate(self.layers):
            h = lin(h)
            if i < n - 1:
                h = ag.relu(h)
        return h

    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for i, lin in enumerate(self.layers):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, x) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for k, v in self.proj_in.named_params().items():
+ added
    def forward(self, x) -> Tensor:
        h = self.proj_in(x)
        for blk in self.blocks:
            r = h
            z = blk["ln"](h)
            z = blk["fc1"](z)
            z = ag.gelu(z)
            z = blk["fc2"](z)
            h = ag.add(r, z)
        return self.proj_out(h)

    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for k, v in self.proj_in.named_params().items():

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def forward(self, X, training: bool = True) -> Tensor:
        # TODO: implement (compose ag.* ops). See the docstring/contract.
        raise NotImplementedError("forward")
    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for name in ("conv1", "bn1", "conv2", "bn2", "head"):
+ added
    def forward(self, X, training: bool = True) -> Tensor:
        h = ag.relu(self.bn1(self.conv1(X), training=training))
        h = ag.avgpool2d(h, 2)
        h = ag.relu(self.bn2(self.conv2(h), training=training))
        h = ag.maxpool2d(h, 2)
        n = h.shape[0]
        h = ag.reshape(h, (n, self.W * 2 * self.side * self.side))
        return self.head(h)

    def named_params(self) -> Dict[str, Tensor]:
        d: Dict[str, Tensor] = {}
        for name in ("conv1", "bn1", "conv2", "bn2", "head"):

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now the robustness helpers in nn.py:

/app/submission/nn.py

− removed
    # TODO: implement (numpy only). See docstring.
    raise NotImplementedError("balanced_group_weights")
+ added
    gids = np.asarray(group_ids).astype(np.int64).reshape(-1)
    if n_groups is None:
        n_groups = int(gids.max()) + 1
    present = np.unique(gids)
    w = np.zeros(int(n_groups), dtype=np.float64)
    w[present] = 1.0 / len(present)
    return w

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    # TODO: implement (numpy only). See docstring.
    raise NotImplementedError("class_balanced_weights")
+ added
    t = np.asarray(targets).astype(np.int64).reshape(-1)
    if n_classes is None:
        n_classes = int(t.max()) + 1
    counts = np.bincount(t, minlength=int(n_classes)).astype(np.float64)
    if beta == 0.0:
        cw = np.where(counts > 0, 1.0 / np.where(counts > 0, counts, 1.0), 0.0)
    else:
        eff = (1.0 - beta ** counts) / (1.0 - beta)
        cw = np.where(counts > 0, 1.0 / np.where(eff > 0, eff, 1.0), 0.0)
    w = cw[t]
    w = w / w.mean()
    return w

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    # TODO: implement (numpy only). See docstring.
    raise NotImplementedError("log_class_prior")
+ added
    t = np.asarray(targets).astype(np.int64).reshape(-1)
    if n_classes is None:
        n_classes = int(t.max()) + 1
    counts = np.bincount(t, minlength=int(n_classes)).astype(np.float64)
    N = len(t)
    prior = counts / N
    return np.where(counts > 0, np.log(np.where(prior > 0, prior, 1.0)), np.log(eps))

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    # TODO: implement (numpy only). See docstring.
    raise NotImplementedError("ldam_margins")
+ added
    t = np.asarray(targets).astype(np.int64).reshape(-1)
    if n_classes is None:
        n_classes = int(t.max()) + 1
    counts = np.bincount(t, minlength=int(n_classes)).astype(np.float64)
    inv = np.where(counts > 0, np.where(counts > 0, counts, 1.0) ** (-0.25), 0.0)
    mx = inv.max()
    if mx <= 0:
        return np.zeros(int(n_classes), dtype=np.float64)
    return inv / mx * max_margin

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    # TODO: implement (numpy only). See docstring.
    raise NotImplementedError("effective_number_weights")
+ added
    t = np.asarray(targets).astype(np.int64).reshape(-1)
    if n_classes is None:
        n_classes = int(t.max()) + 1
    counts = np.bincount(t, minlength=int(n_classes)).astype(np.float64)
    present = counts > 0
    eff = (1.0 - beta ** counts) / (1.0 - beta)
    w = np.where(present, 1.0 / np.where(eff > 0, eff, 1.0), 0.0)
    w = w / w[present].mean()
    return w

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def update(self, group_losses, present=None):
        # TODO: implement the masked EMA update (see docstring). Return self.l.copy().
        raise NotImplementedError("EMAGroupLoss.update")

    def worst_group(self):
        # TODO: implement (argmax of the current EMA). See docstring.
        raise NotImplementedError("EMAGroupLoss.worst_group")
+ added
    def update(self, group_losses, present=None):
        new = np.asarray(group_losses, dtype=np.float64).reshape(-1)
        if present is None:
            mask = np.ones(self.n_groups, dtype=bool)
        else:
            mask = np.asarray(present, dtype=bool).reshape(-1)
        for k in range(self.n_groups):
            if not mask[k]:
                continue
            if not self._init[k]:
                self.l[k] = new[k]
                self._init[k] = True
            else:
                self.l[k] = self.beta * self.l[k] + (1.0 - self.beta) * new[k]
        return self.l.copy()

    def worst_group(self):
        return int(np.argmax(self.l))

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/nn.py

− removed
    def update(self, group_losses):
        # TODO: exponentiated-gradient update of self.q on group_losses; renormalize.
        raise NotImplementedError("GroupDROState.update")
+ added
    def update(self, group_losses):
        loss = np.asarray(group_losses, dtype=np.float64).reshape(-1)
        self.q = self.q * np.exp(self.eta_q * loss)
        self.q = self.q / self.q.sum()
        return self.q.copy()

contents
The file /app/submission/nn.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now data.py:

/app/submission/data.py

− removed
    """Flatten (y, g) to a single group id y*n_classes + g (int64)."""
    # TODO
    raise NotImplementedError("group_ids")
+ added
    """Flatten (y, g) to a single group id y*n_classes + g (int64)."""
    return (np.asarray(y, dtype=np.int64) * int(n_classes) + np.asarray(g, dtype=np.int64)).astype(np.int64)

contents
The file /app/submission/data.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/data.py

− removed
    """Yield (Xb, yb, gb) minibatches over a random permutation of the dataset."""
    # TODO
    raise NotImplementedError("iterate")
+ added
    """Yield (Xb, yb, gb) minibatches over a random permutation of the dataset."""
    X = np.asarray(X); y = np.asarray(y); g = np.asarray(g)
    n = X.shape[0]
    perm = rng.permutation(n)
    for i in range(0, n, batch_size):
        idx = perm[i:i + batch_size]
        yield X[idx], y[idx], g[idx]

contents
The file /app/submission/data.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/data.py

− removed
    """Return (min over (y,g) groups of within-group accuracy, average accuracy, per-group dict)."""
    # TODO
    raise NotImplementedError("worst_group_acc")
+ added
    """Return (min over (y,g) groups of within-group accuracy, average accuracy, per-group dict)."""
    preds = np.asarray(preds).reshape(-1)
    y = np.asarray(y).reshape(-1)
    g = np.asarray(g).reshape(-1)
    correct = (preds == y)
    gid = y * int(n_classes) + g
    per = {}
    for k in np.unique(gid):
        mask = gid == k
        per[int(k)] = float(correct[mask].mean())
    wga = min(per.values()) if per else 0.0
    avg = float(correct.mean()) if len(correct) else 0.0
    return wga, avg, per

contents
The file /app/submission/data.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/data.py

− removed
    """Boolean mask selecting ~frac of EACH (y,g) group (keeps both slices group-balanced)."""
    # TODO
    raise NotImplementedError("stratified_group_split")
+ added
    """Boolean mask selecting ~frac of EACH (y,g) group (keeps both slices group-balanced)."""
    y = np.asarray(y).reshape(-1)
    g = np.asarray(g).reshape(-1)
    gid = y * int(n_classes) + g
    mask = np.zeros(len(y), dtype=bool)
    for k in np.unique(gid):
        idx = np.where(gid == k)[0]
        rng.shuffle(idx)
        ntake = int(round(frac * len(idx)))
        ntake = max(0, min(len(idx), ntake))
        mask[idx[:ntake]] = True
    return mask

contents
The file /app/submission/data.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now let me run the full check suite:

Run full check suite

shell
OMP_NUM_THREADS=1 python3 run_checks.py 2>&1 | grep -E "FAIL|TOTAL|^\[|^---|^[a-z].*[0-9]/[0-9]" | head -60
output
[autograd_grads]  81/81
[nn_forward]  21/21
[optim]  21/21
[robust]  13/13
[robust2]  8/8
[data]  3/3
----------------------------------------------------------------------
autograd_grads 81/81 | nn_forward 21/21 | optim 21/21 | robust 13/13 | robust2 8/8 | data 3/3
TOTAL  147/147 public checks passing
All 147 public checks pass. Now let me write the training recipe. Let me save progress to memory first, then write `train.py`.
write · /app/submission/train.py
"""Training entry point: worst-group-robust SmallCNN via ERM pretrain + DFR last-layer retrain.

Recipe:
  1. ERM-train the full SmallCNN on the (spuriously correlated) train split with AdamW + grad clip.
     This learns a feature extractor that encodes the shape (among other things) and populates the
     BatchNorm running buffers used at eval time.
  2. DFR: freeze the extractor, recompute penultimate features (eval/BN-eval mode) on the
     GROUP-BALANCED reweight split, and re-fit ONLY the linear classifier with a group-balanced
     (group_weighted_ce) loss so the head stops keying off the spurious background color.
  3. Save the pinned-architecture checkpoint the grader loads.
"""
from __future__ import annotations

import argparse
import json
import os
import sys

import numpy as np

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
sys.path.insert(0, "/app")
sys.path.insert(0, "/app/submission")

import autograd as ag          # noqa: E402,F401
from autograd import Tensor    # noqa: E402
import data as D               # noqa: E402,F401
import optim as O              # noqa: E402,F401
import nn as NN                # noqa: E402
from nn import SmallCNN        # noqa: E402,F401

# Pinned architecture (MUST match the grader's reference; do not change).
WIDTH = 16
EMBED_DIM = 48


def save_checkpoint(path, state_dict, n_classes, img_size):
    os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
    arrs = {k: np.asarray(v, dtype=np.float32) for k, v in s
…[truncated 5205 chars]

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)
Let me do a quick smoke run with fewer epochs to verify the pipeline works end-to-end:

Smoke train 3 epochs

shell
cd /app/submission && OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 timeout 300 python3 train.py --epochs 3 2>&1 | tail -20
output
(Bash completed with no output)

Smoke train unbuffered

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 timeout 300 python3 -u train.py --epochs 3 2>&1 | tail -20; echo "EXIT=${PIPESTATUS[0]}"
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
EXIT=137

Time 5 batches and memory

shell
OMP_NUM_THREADS=1 python3 -u -c "
import time,numpy as np, resource
import autograd as ag, optim as O
from autograd import Tensor
import data as D
from nn import SmallCNN
Xtr,ytr,gtr=D.load_npz('/app/data/train.npz')
m=SmallCNN(n_classes=4,img_size=16,width=16,embed_dim=48,seed=0)
p=m.params()
opt=O.AdamW(p,lr=1e-3,weight_decay=1e-4)
t0=time.time()
bs=128
for i in range(5):
    xb=Xtr[i*bs:(i+1)*bs]; yb=ytr[i*bs:(i+1)*bs]
    opt.zero_grad()
    loss=ag.cross_entropy(m(xb,training=True),yb)
    loss.backward()
    O.clip_grad_norm(p,5.0)
    opt.step()
    print('batch',i,'loss',float(loss.data),'t',round(time.time()-t0,2),'mem_MB',round(resource.getrusage(resource.RUSAGE_SELF).ru_maxrss/1024,1))
" 2>&1 | tail -20
output
batch 0 loss 1.5429725751578092 t 0.35 mem_MB 126.4
batch 1 loss 1.3161780557628497 t 0.76 mem_MB 195.3

Check memory with gc.collect

shell
free -m 2>/dev/null | head -3; echo "---"; OMP_NUM_THREADS=1 python3 -u -c "
import time,numpy as np, resource, gc
import autograd as ag, optim as O
from nn import SmallCNN
import data as D
Xtr,ytr,gtr=D.load_npz('/app/data/train.npz')
m=SmallCNN(n_classes=4,img_size=16,width=16,embed_dim=48,seed=0)
p=m.params(); opt=O.AdamW(p,lr=1e-3,weight_decay=1e-4)
bs=128
for i in range(12):
    xb=Xtr[i*bs:(i+1)*bs]; yb=ytr[i*bs:(i+1)*bs]
    opt.zero_grad()
    loss=ag.cross_entropy(m(xb,training=True),yb); loss.backward()
    O.clip_grad_norm(p,5.0); opt.step()
    del loss; gc.collect()
    print('batch',i,'mem_MB',round(resource.getrusage(resource.RUSAGE_SELF).ru_maxrss/1024,1),flush=True)
" 2>&1 | tail -20
output
total        used        free      shared  buff/cache   available
Mem:             481         250         180           1          65         231
Swap:              0           0           0
---
batch 0 mem_MB 126.4
batch 1 mem_MB 129.0
batch 2 mem_MB 129.0
batch 3 mem_MB 129.3
batch 4 mem_MB 129.3
batch 5 mem_MB 129.3
batch 6 mem_MB 129.3
batch 7 mem_MB 129.3
batch 8 mem_MB 129.3
batch 9 mem_MB 129.3
batch 10 mem_MB 129.3
batch 11 mem_MB 129.3
The machine has only 481MB RAM , reference cycles in the graph cause OOM. `gc.collect()` per batch keeps it stable at 129MB. Let me add that to the training loops.

/app/submission/train.py

− removed
import argparse
import json
import os
import sys

import numpy as np
+ added
import argparse
import gc
import json
import os
import sys

import numpy as np

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/train.py

− removed
            O.clip_grad_norm(params, 5.0)
            opt.step()
            step += 1
    return model
+ added
            O.clip_grad_norm(params, 5.0)
            opt.step()
            del logits, loss
            gc.collect()
            step += 1
    return model

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/train.py

− removed
            loss = ag.group_weighted_ce(logits, y, gid)
            loss.backward()
            opt.step()
        Wsum += W.data
+ added
            loss = ag.group_weighted_ce(logits, y, gid)
            loss.backward()
            opt.step()
            del logits, loss
            gc.collect()
        Wsum += W.data

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/train.py

− removed
        f = model.featurize(xb, training=training)
        feats.append(np.asarray(f.data))
    return np.concatenate(feats, axis=0)
+ added
        f = model.featurize(xb, training=training)
        feats.append(np.asarray(f.data))
        del f
        gc.collect()
    return np.concatenate(feats, axis=0)

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)

/app/submission/train.py

− removed
        out.append(np.asarray(model(xb, training=False).data))
    return np.concatenate(out, axis=0)
+ added
        out.append(np.asarray(model(xb, training=False).data))
        gc.collect()
    return np.concatenate(out, axis=0)

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now let me run a moderate training in the background and monitor:

Launch training in background

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u train.py --epochs 20 > /app/train.out 2>&1 &
echo "started pid $!"
output
started pid 1521

Check training progress after 90s

shell
sleep 90; cat /app/train.out; echo "---running?---"; ps aux | grep "[t]rain.py" | awk '{print $6/1024" MB"}'
output
<tool_use_error>Blocked: sleep 90 followed by: cat /app/train.out echo "---running?---" ps aux grep "[t]rain.py" awk '{print $6/1024" MB"}'. To wait for a condition, use Monitor with an until-loop (e.g. `until <check>; do sleep 2; done`). To wait for a command you started, use run_in_background: true. Do not chain shorter sleeps to work around this block.</tool_use_error>

Wait until ERM done or process exits

shell
until ! ps -p 1521 > /dev/null 2>&1 || grep -q "Phase 2" /app/train.out 2>/dev/null; do sleep 5; done; cat /app/train.out; echo "---mem---"; ps aux | grep "[t]rain.py" | awk '{print $6/1024" MB"}'
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
  ERM head on reweight: worst-group=0.000 avg=0.352
Phase 2: DFR last-layer retrain ...
---mem---
0.101562 MB
233.605 MB
112.422 MB

Wait for training completion

shell
until ! ps -p 1521 > /dev/null 2>&1; do sleep 5; done; cat /app/train.out
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
  ERM head on reweight: worst-group=0.000 avg=0.352
Phase 2: DFR last-layer retrain ...
  DFR head val: worst-group=0.625 avg=0.805
  Final model on reweight: worst-group=0.600 avg=0.824
saved checkpoint -> /app/submission/model.npz
DFR lifts worst-group from 0 to 0.6, but I should push higher. The frozen ERM features limit it. Let me try fine-tuning the whole network on the balanced set. Let me build a dev harness to measure, loading the existing checkpoint to skip re-running ERM:
write · /app/submission/exp.py
"""Dev harness: experiment with full-network fine-tuning on the balanced reweight set."""
import gc, sys, os, numpy as np
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import autograd as ag, optim as O, data as D
from autograd import Tensor
from nn import SmallCNN

def load_ckpt(path, n_classes, img_size):
    d = np.load(path)
    sd = {k: d[k] for k in d.files if k != "__config__"}
    m = SmallCNN(n_classes=n_classes, img_size=img_size, width=16, embed_dim=48, seed=0)
    m.load_state_dict(sd)
    return m

def worst_group(preds, y, g, nc):
    gid = y*nc+g; accs=[]
    for k in np.unique(gid):
        mm=gid==k; accs.append((preds[mm]==y[mm]).mean())
    return float(min(accs)), float((preds==y).mean())

def logits_batched(m, X, bs=256):
    out=[]
    for i in range(0,X.shape[0],bs):
        out.append(np.asarray(m(X[i:i+bs],training=False).data)); gc.collect()
    return np.concatenate(out,0)

def finetune(m, X, y, g, nc, epochs, lr, bs=128, seed=0, wd=1e-4):
    rng=np.random.default_rng(seed)
    p=m.params(); opt=O.AdamW(p, lr=lr, weight_decay=wd)
    N=X.shape[0]; nsteps=epochs*((N+bs-1)//bs); step=0
    gid_all=(y*nc+g).astype(np.int64)
    for ep in range(epochs):
        perm=rng.permutation(N)
        for i in range(0,N,bs):
            idx=perm[i:i+bs]
            opt.lr=O.cosine_lr(step,nsteps,lr,warmup=max(1,nsteps//20),min_lr=lr*0.05)
            opt.zero_grad()
            logits=m(X[idx],training=True)
            loss=ag.group_weighted_ce
…[truncated 863 chars]

contents
File created successfully at: /app/submission/exp.py (file state is current in your context , no need to Read it back)

Run fine-tune experiment in background

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u exp.py > /app/exp.out 2>&1 & echo "pid $!"
output
pid 1619

Wait for experiment

shell
until ! ps -p 1619 > /dev/null 2>&1; do sleep 5; done; cat /app/exp.out
output
before ft val (0.5833333333333334, 0.8333333333333334)
after 5 epochs val (0.6666666666666666, 0.875)
after 10 epochs val (0.7916666666666666, 0.9114583333333334)
after 15 epochs val (0.75, 0.9270833333333334)
after 20 epochs val (0.75, 0.9427083333333334)
after 25 epochs val (0.7916666666666666, 0.9453125)
after 30 epochs val (0.7916666666666666, 0.953125)
Whole-network fine-tuning on balanced data reaches ~0.79 worst-group / 0.95 avg , much better than DFR alone. Let me check whether a DFR head on top of the fine-tuned extractor helps further, and test longer fine-tuning:

/app/submission/exp.py

− removed
    for stint in range(6):
        finetune(m, Xrw[fit_mask], yrw[fit_mask], grw[fit_mask], nc, epochs=5, lr=3e-4, seed=stint)
        vp=logits_batched(m,Xrw[val_mask]).argmax(1)
        print(f'after {5*(stint+1)} epochs val', worst_group(vp,yrw[val_mask],grw[val_mask],nc), flush=True)
+ added
    for stint in range(8):
        finetune(m, Xrw[fit_mask], yrw[fit_mask], grw[fit_mask], nc, epochs=5, lr=3e-4, seed=stint)
        vp=logits_batched(m,Xrw[val_mask]).argmax(1)
        print(f'after {5*(stint+1)} epochs val', worst_group(vp,yrw[val_mask],grw[val_mask],nc), flush=True)
    # DFR head refit on top of fine-tuned extractor
    def featb(X,bs=256):
        fs=[]
        for i in range(0,X.shape[0],bs):
            fs.append(np.asarray(m.featurize(X[i:i+bs],training=False).data)); gc.collect()
        return np.concatenate(fs,0)
    Ff=featb(Xrw[fit_mask]); Fv=featb(Xrw[val_mask])
    gidf=(yrw[fit_mask]*nc+grw[fit_mask]).astype(np.int64)
    W=Tensor(np.random.default_rng(0).standard_normal((48,nc))*0.01,requires_grad=True)
    b=Tensor(np.zeros(nc),requires_grad=True)
    opt=O.AdamW([W,b],lr=5e-2,weight_decay=1e-3)
    for s in range(500):
        opt.zero_grad(); lo=ag.add(ag.matmul(Tensor(Ff),W),b)
        loss=ag.group_weighted_ce(lo,yrw[fit_mask],gidf); loss.backward(); opt.step(); del lo,loss; gc.collect()
    vp=(Fv@W.data+b.data).argmax(1)
    print('DFR-on-finetuned val', worst_group(vp,yrw[val_mask],grw[val_mask],nc), flush=True)

contents
The file /app/submission/exp.py has been updated successfully. (file state is current in your context , no need to Read it back)

Run extended fine-tune + DFR experiment

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u exp.py > /app/exp.out 2>&1 & echo "pid $!"
output
pid 1654
While that runs, let me record key context to memory about the environment constraints.
write · /home/user/.claude/projects/-app/memory/MEMORY.md
- [numpy-dl-framework-task](numpy-dl-framework-task.md) , from-scratch numpy autodiff + worst-group robust SmallCNN training task in /app

contents
File created successfully at: /home/user/.claude/projects/-app/memory/MEMORY.md (file state is current in your context , no need to Read it back)
write · /home/user/.claude/projects/-app/memory/numpy-dl-framework-task.md
---
name: numpy-dl-framework-task
description: Constraints and recipe for the /app numpy-only DL framework + worst-group robust training task
metadata:
  type: project
---

Task in `/app`: implement numpy-only reverse-mode autodiff framework (`submission/autograd.py`,
`nn.py`, `optim.py`, `data.py`) then train worst-group-robust SmallCNN -> `submission/model.npz`.
Check with `python3 /app/run_checks.py` (147 public checks). All 147 pass as of this session.

**Hard env constraints:**
- Machine has only ~481MB RAM. The autograd graph creates reference cycles (`out._backward`
  closure captures `out`), so **`gc.collect()` per training batch is required** or the run OOMs
  (SIGKILL/exit 137). With gc.collect each batch, memory stays ~129MB.
- Set `OMP_NUM_THREADS=1` etc. float64 throughout. ~0.4s/batch for SmallCNN bs=128.
- ARG_MAX 65536 , write large files in pieces.

**Data:** train.npz (2400, spurious color~shape ~97%), reweight.npz (1280, group-balanced 80/group,
16 groups = y*4+g). 4 shape classes, 4 colors, 16x16x3 images in [0,1]. Feed raw X (no input
normalization , grader feeds raw; rely on BN).

**Recipe:** ERM pretrain on train -> fine-tune WHOLE net on balanced reweight with
group_weighted_ce (this beats DFR-head-only: ~0.79 worst-group val vs 0.6 for DFR alone).
SmallCNN pinned width=16 embed_dim=48; chose **maxpool2d** for the intermediate "pool" (ambiguous
in spec , risk if grader uses avgpool).

contents
File created successfully at: /home/user/.claude/projects/-app/memory/numpy-dl-framework-task.md (file state is current in your context , no need to Read it back)

Wait for experiment results

shell
until ! ps -p 1654 > /dev/null 2>&1; do sleep 5; done; cat /app/exp.out
output
before ft val (0.5833333333333334, 0.8333333333333334)
after 5 epochs val (0.6666666666666666, 0.875)
after 10 epochs val (0.7916666666666666, 0.9114583333333334)
after 15 epochs val (0.75, 0.9270833333333334)
after 20 epochs val (0.75, 0.9427083333333334)
after 25 epochs val (0.7916666666666666, 0.9453125)
after 30 epochs val (0.7916666666666666, 0.953125)
after 35 epochs val (0.9166666666666666, 0.96875)
after 40 epochs val (0.9166666666666666, 0.9713541666666666)
DFR-on-finetuned val (0.875, 0.9583333333333334)
40 fine-tune epochs reaches 0.917 worst-group / 0.97 avg on held-out val , strong. The stint structure (cosine restarts) helped. Let me rewrite `train.py` to the final recipe: ERM pretrain + whole-net balanced fine-tune in stints, with an honest val estimate and final training on all data.
write · /app/submission/train.py
"""Training entry point: worst-group-robust SmallCNN.

Recipe:
  1. ERM-pretrain the full SmallCNN on the (spuriously correlated) train split (AdamW + grad clip)
     to learn general conv features and seed BatchNorm running buffers.
  2. Fine-tune the WHOLE network on the GROUP-BALANCED reweight split with the group-balanced
     (group_weighted_ce) loss, in several short cosine "stints". Because the balanced data carries
     no background-color->shape signal, this drives the network to predict the SHAPE, lifting
     worst-group accuracy far above the ERM baseline (and above last-layer-only DFR).
  3. Save the pinned-architecture checkpoint the grader loads.

A held-out group-stratified split of the reweight set is used only to PRINT an honest worst-group
estimate; the saved model is fine-tuned on ALL of the reweight set.
"""
from __future__ import annotations

import argparse
import gc
import json
import os
import sys

import numpy as np

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
sys.path.insert(0, "/app")
sys.path.insert(0, "/app/submission")

import autograd as ag          # noqa: E402,F401
from autograd import Tensor    # noqa: E402,F401
import data as D               # noqa: E402,F401
import optim as O              # noqa: E402,F401
from nn import SmallCNN        # noqa: E402

WIDTH = 16
EMBED_DIM = 48


def save_checkpoint(path, state_dict, n_classes, img_size):
    os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
    arrs = {k: np.asarra
…[truncated 4756 chars]

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)
Now let me run the final training:

Run final training in background

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u train.py > /app/train.out 2>&1 & echo "pid $!"
output
pid 1691

Wait for VAL estimate

shell
until ! ps -p 1691 > /dev/null 2>&1 || grep -q "VAL worst" /app/train.out 2>/dev/null; do sleep 10; done; cat /app/train.out
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
  ERM worst-group/avg on reweight: (0.0, 0.284375)
Phase 2a: validation estimate (fine-tune on fit split) ...
  VAL worst-group/avg: (0.7916666666666666, 0.9401041666666666)
Phase 2b: final fine-tune on ALL reweight ...

Wait for training completion

shell
until ! ps -p 1691 > /dev/null 2>&1; do sleep 10; done; cat /app/train.out; echo "---"; ls -la /app/submission/model.npz
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
  ERM worst-group/avg on reweight: (0.0, 0.284375)
Phase 2a: validation estimate (fine-tune on fit split) ...
  VAL worst-group/avg: (0.7916666666666666, 0.9401041666666666)
Phase 2b: final fine-tune on ALL reweight ...
  FINAL (in-sample) worst-group/avg on reweight: (0.9375, 0.9875)
saved checkpoint -> /app/submission/model.npz
---
-rw-r--r-- 1 user user 71712 Jun 30 23:11 /app/submission/model.npz
Final model saved with in-sample 0.94, held-out val 0.79. Let me inspect the data to see if augmentation is safe, then try to push worst-group higher with combined data + augmentation.

Inspect image structure for augmentation

shell
OMP_NUM_THREADS=1 python3 -c "
import numpy as np
d=np.load('/app/data/reweight.npz'); X,y,g=d['X'],d['y'],d['g']
# For each class, look at a sample image's structure (mean over channels), and color signature
for cls in range(4):
    i=np.where(y==cls)[0][0]
    img=X[i]
    print('class',cls,'g',g[i],'channel means',np.round(img.reshape(3,-1).mean(1),3),'shape-map nonzero frac', round(float((img.max(0)>0.1).mean()),3))
# check if shape occupies whole image or a tile
print('img min/max', X.min(), X.max())
# symmetry check: is a class image roughly symmetric under flips?
i=np.where(y==0)[0][0]; im=X[i].max(0)
print('hflip diff', round(float(np.abs(im-im[:,::-1]).mean()),4),'vflip diff',round(float(np.abs(im-im[::-1]).mean()),4))
"
output
class 0 g 1 channel means [0.285 0.489 0.823] shape-map nonzero frac 1.0
class 1 g 0 channel means [0.802 0.236 0.236] shape-map nonzero frac 1.0
class 2 g 0 channel means [0.794 0.236 0.235] shape-map nonzero frac 1.0
class 3 g 0 channel means [0.792 0.233 0.232] shape-map nonzero frac 1.0
img min/max 0.0 1.0
hflip diff 0.0709 vflip diff 0.075
Whole image is filled with background color + a shape drawn on top; shapes are roughly but not perfectly flip-symmetric (class-preserving flips are safe for geometric shapes). Let me experiment with flip augmentation and combined group-balanced sampling to improve generalization:
write · /app/submission/exp2.py
"""Dev: compare fine-tune variants (flip aug, combined balanced sampling) on a fixed val split."""
import gc, sys, os, numpy as np
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
import autograd as ag, optim as O, data as D
from nn import SmallCNN

NC=4; IMG=16

def wg(preds,y,g):
    gid=y*NC+g; a=[(preds[gid==k]==y[gid==k]).mean() for k in np.unique(gid)]
    return float(min(a)), float((preds==y).mean())

def logits_b(m,X,bs=256):
    o=[]
    for i in range(0,X.shape[0],bs):
        o.append(np.asarray(m(X[i:i+bs],training=False).data)); gc.collect()
    return np.concatenate(o,0)

def aug(xb, rng):
    xb=xb.copy()
    h=rng.random(xb.shape[0])<0.5; v=rng.random(xb.shape[0])<0.5
    xb[h]=xb[h,:,:,::-1]; xb[v]=xb[v,:,::-1,:]
    return xb

def erm(m,X,y,epochs,seed):
    rng=np.random.default_rng(seed); p=m.params(); opt=O.AdamW(p,lr=1e-3,weight_decay=1e-4)
    N=X.shape[0]; ns=epochs*((N+127)//128); st=0
    for ep in range(epochs):
        perm=rng.permutation(N)
        for i in range(0,N,128):
            idx=perm[i:i+128]; opt.lr=O.cosine_lr(st,ns,1e-3,warmup=max(1,ns//20),min_lr=2e-5)
            opt.zero_grad(); l=ag.cross_entropy(m(X[idx],training=True),y[idx]); l.backward()
            O.clip_grad_norm(p,5.0); opt.step(); del l; gc.collect(); st+=1
    return m

def ft_reweight(m,X,y,gid,stints,ep,lr,seed,use_aug=False):
    rng=np.random.default_rng(seed); p=m.params()
    for s in range(stints):
        opt=O.AdamW(p,lr=lr,weight_decay=1e-4); N=
…[truncated 2767 chars]

contents
File created successfully at: /app/submission/exp2.py (file state is current in your context , no need to Read it back)

Run variant comparison experiment

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u exp2.py > /app/exp2.out 2>&1 & echo "pid $!"
output
pid 1806

Wait for variant experiment

shell
until ! ps -p 1806 > /dev/null 2>&1; do sleep 10; done; cat /app/exp2.out
output
reweight-only       (0.75, 0.9453125)
reweight+aug        (0.25, 0.8411458333333334)
combined-balanced   (0.875, 0.9713541666666666)
combined-bal+aug    (0.75, 0.9505208333333334)
Key findings: flip augmentation **hurts** (shapes are orientation-dependent , flips break labels), but **combined group-balanced sampling** over train+reweight gives the best val worst-group (0.875 vs 0.75). Let me adopt that as the final recipe.
write · /app/submission/train.py
"""Training entry point: worst-group-robust SmallCNN.

Recipe (validated on a held-out group-stratified split of the reweight set):
  1. ERM-pretrain the full SmallCNN on the (spuriously correlated) train split (AdamW + grad clip)
     to learn general conv features and seed BatchNorm running buffers.
  2. Fine-tune the WHOLE network with GROUP-BALANCED minibatch sampling over the COMBINED
     train+reweight pool: every minibatch draws an equal number of samples from each (shape,color)
     group, so the background color carries no class signal and the network must predict the SHAPE.
     This lifts worst-group accuracy far above the ERM baseline and above reweight-only fine-tuning.
  3. Save the pinned-architecture checkpoint the grader loads.

(Image augmentation via flips was tried and REMOVED -- the shapes are orientation-dependent, so
flips are not label-preserving and hurt worst-group accuracy.)
"""
from __future__ import annotations

import argparse
import gc
import json
import os
import sys

import numpy as np

sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
sys.path.insert(0, "/app")
sys.path.insert(0, "/app/submission")

import autograd as ag          # noqa: E402,F401
from autograd import Tensor    # noqa: E402,F401
import data as D               # noqa: E402,F401
import optim as O              # noqa: E402,F401
from nn import SmallCNN        # noqa: E402

WIDTH = 16
EMBED_DIM = 48


def save_checkpoint(path, state_dict, n_classes, img_size):
    os
…[truncated 5345 chars]

contents
The file /app/submission/train.py has been updated successfully. (file state is current in your context , no need to Read it back)

Run final training with combined-balanced recipe

shell
OMP_NUM_THREADS=1 OPENBLAS_NUM_THREADS=1 MKL_NUM_THREADS=1 nohup python3 -u train.py > /app/train.out 2>&1 & echo "pid $!"
output
pid 1944
While the final training runs, let me re-run the full check suite to confirm nothing regressed:

Re-run full check suite

shell
cd /app && OMP_NUM_THREADS=1 python3 run_checks.py 2>&1 | tail -8
output
data/group_ids                             OK    ([ 1  4 11 14])
  data/worst_group_acc                       OK    (wga=0.00 avg=0.80)
  data/stratified_group_split                OK    (selected 33/60)

----------------------------------------------------------------------
autograd_grads 81/81 | nn_forward 21/21 | optim 21/21 | robust 13/13 | robust2 8/8 | data 3/3
TOTAL  147/147 public checks passing
All public checks pass. Now make sure model.npz clears the held-out worst-group accuracy threshold; the grader re-checks with DIFFERENT seeds.

Wait for final training

shell
until ! ps -p 1944 > /dev/null 2>&1; do sleep 10; done; cat /app/train.out
output
n_classes=4 img_size=16 train=(2400, 3, 16, 16) reweight=(1280, 3, 16, 16)
Phase 1: ERM pretrain ...
  ERM worst-group/avg on reweight: (0.0, 0.26015625)
Phase 2a: validation estimate (balanced fine-tune on train+reweight_fit) ...
  VAL worst-group/avg: (0.875, 0.9765625)
Phase 2b: final balanced fine-tune on train+ALL reweight ...
  FINAL (in-sample) worst-group/avg on reweight: (0.9625, 0.99453125)
saved checkpoint -> /app/submission/model.npz
Val worst-group is now **0.875** (avg 0.977) , a strong result. Let me verify the saved checkpoint loads cleanly into a fresh SmallCNN (mimicking the grader) and reproduces the accuracy:

Verify checkpoint loads strict and evaluate

shell
cd /app/submission && OMP_NUM_THREADS=1 python3 -c "
import numpy as np, json, gc
import data as D
from nn import SmallCNN
d=np.load('model.npz')
cfg=json.loads(bytes(d['__config__']).decode()); print('config',cfg)
sd={k:d[k] for k in d.files if k!='__config__'}
m=SmallCNN(n_classes=cfg['n_classes'],img_size=cfg['img_size'],width=cfg['width'],embed_dim=cfg['embed_dim'],seed=999)
m.load_state_dict(sd, strict=True)  # grader-style strict load into a DIFFERENT seed
print('loaded strict OK; keys=',len(sd))
Xrw,yrw,grw=D.load_npz('/app/data/reweight.npz')
o=[]
for i in range(0,len(Xrw),256):
    o.append(np.asarray(m(Xrw[i:i+256],training=False).data)); gc.collect()
pred=np.concatenate(o,0).argmax(1)
gid=yrw*4+grw; accs={int(k):float((pred[gid==k]==yrw[gid==k]).mean()) for k in np.unique(gid)}
print('worst-group',min(accs.values()),'avg',float((pred==yrw).mean()))
print('per-group',{k:round(v,2) for k,v in sorted(accs.items())})
print('param shapes ok:', all(sd[k].shape==v.data.shape for k,v in m.named_params().items()))
"
output
config {'n_classes': 4, 'img_size': 16, 'width': 16, 'embed_dim': 48}
loaded strict OK; keys= 22
worst-group 0.9625 avg 0.99453125
per-group {0: 1.0, 1: 1.0, 2: 1.0, 3: 0.99, 4: 1.0, 5: 1.0, 6: 1.0, 7: 1.0, 8: 1.0, 9: 0.97, 10: 0.96, 11: 0.99, 12: 1.0, 13: 1.0, 14: 1.0, 15: 1.0}
param shapes ok: True
Excellent , checkpoint loads strict into a fresh model and all 16 groups are ≥0.96 in-sample (val held-out was 0.875). Let me clean up dev files and verify no forbidden imports anywhere in the submission:

Clean dev files and scan forbidden imports

shell
rm -f exp.py exp2.py && rm -rf __pycache__ && echo "removed dev files" && echo "--- forbidden import scan ---" && grep -rEl "torch|tensorflow|jax|tinygrad|micrograd|autograd_lib|chainer|flax|keras|theano|cupy|mxnet|^import autograd\b" *.py | xargs -r grep -nE "import (torch|tensorflow|jax|tinygrad|chainer|flax|keras|theano|cupy|mxnet)" || echo "NONE found"; echo "--- files ---"; ls -la
output
removed dev files
--- forbidden import scan ---
NONE found
--- files ---
total 196
drwxr-xr-x 2 user user  4096 Jun 30 23:28 .
drwxr-xr-x 4 user user  4096 Jun 30 23:12 ..
-rw-r--r-- 1 user user 57692 Jun 30 22:53 autograd.py
-rw-r--r-- 1 user user  2570 Jun 30 22:56 data.py
-rw-r--r-- 1 user user 71712 Jun 30 23:28 model.npz
-rw-r--r-- 1 user user 25713 Jun 30 22:56 nn.py
-rw-r--r-- 1 user user 15868 Jun 30 22:54 optim.py
-rw-r--r-- 1 user user  6845 Jun 30 23:22 train.py
Now let me run the env smoke test and the final full check suite to confirm everything is green:

Run smoke test and full checks

shell
cd /app && bash test.sh 2>&1 | tail -6; echo "=== FULL CHECKS ==="; OMP_NUM_THREADS=1 python3 run_checks.py 2>&1 | tail -4
output
numpy 2.2.6
----------------------------------------------------------------------
autograd_grads 81/81 | nn_forward 21/21 | optim 21/21 | robust 13/13 | robust2 8/8 | data 3/3
TOTAL  147/147 public checks passing
All public checks pass. Now make sure model.npz clears the held-out worst-group accuracy threshold; the grader re-checks with DIFFERENT seeds.
app_test smoke OK (run 'python3 /app/run_checks.py' to test your implementation)
=== FULL CHECKS ===
----------------------------------------------------------------------
autograd_grads 81/81 | nn_forward 21/21 | optim 21/21 | robust 13/13 | robust2 8/8 | data 3/3
TOTAL  147/147 public checks passing
All public checks pass. Now make sure model.npz clears the held-out worst-group accuracy threshold; the grader re-checks with DIFFERENT seeds.
Everything is complete and green. Let me do a final summary of the state. ## Summary I implemented the full numpy-only deep-learning framework and trained a worst-group-robust classifier. All **147/147 public component checks pass** and the trained checkpoint is saved at `/app/submission/model.npz`. ### What was implemented **`autograd.py`** , Reverse-mode autodiff: iterative topological `backward()`, plus correct analytic backward for ~60 ops including broadcasting-aware binary ops, reductions over axis/axis-tuples, `matmul` (batched+broadcast), all activations (gelu/silu/mish/elu/softplus…), stable softmax/log_softmax/CE, the spatial ops (`conv2d` with stride via strided col2im scatter, `maxpool2d`, overlapping `maxpool2d_stride`, `avgpool2d`, `global_avg_pool`, `batchnorm2d` train+eval), the norms (layer/batch/rms/group), and all robustness losses with **per-group-normalized backward** (`group_weighted_ce`, `group_dro_loss`, `reweighted_ce`, `logit_adjusted_ce`, `focal`, `irm`, `gce`, `ldam`, `spectral_decoupling`, `vrex`). **`nn.py`** , All layer/model forwards (Linear, Conv2d, BN1d/2d, Layer/RMS/GroupNorm, pools, SmallCNN+featurize, MLP, ResidualMLP, TinyConvNet, ResidualConvNet) plus the robustness machinery (balanced/class-balanced/effective-number weights, log-prior, ldam-margins, `GroupDROState`, `EMAGroupLoss`). **`optim.py`** , All 10 optimizers, 6 schedulers, both grad clippers (all match reference to 0 error). **`data.py`** , group helpers and stratified s …[truncated 1310 chars]
Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward
tests/test.sh
=== SyncVals verifier (local re-grade of the agent's own checkpoint) ===

COMPONENT CONFORMANCE SUITE: 194/194 cases passed  (all milestones pass: True)
FINAL METRIC: worst-group accuracy = 0.9433  >= threshold 0.86

REWARD = 1   (1 iff every component milestone passes AND the sealed held-out metric clears its threshold)

NOTE: the in-sandbox training in the 481MB e2b box was OOM-killed (0-byte checkpoint), so the raw
in-sandbox reward was an infrastructure artifact. This reward is from a faithful LOCAL re-train of the
agent's OWN train.py (24GB, no OOM) with its own default hyperparameters, then re-graded by the real verifier.

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_e3def5ba1c0f4cc4. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_e3def5ba1c0f4cc4 · verifier authoritative; classifier explanatory.