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 shows: COMPONENT CONFORMANCE SUITE: 194/194 cases passed (all milestones pass: True), FINAL METRIC: worst-group accuracy = 0.91 >= threshold 0.86, REWARD = 1. The verifier note explains that the in-sandbox training was OOM-killed due to sandbox resource limits (481MB), so the local re-grader re-ran the agent's own train.py with adequate memory (24GB) and confirmed all component tests passed and worst-group accuracy exceeded threshold. This indicates the agent's implementation of the framework was correct.
Root causeThe agent successfully implemented a complete numpy-only deep learning framework with reverse-mode autodiff, spatial operations, robustness losses, layers, optimizers, and a training recipe that achieved 0.91 worst-group accuracy on the sealed test set. The in-sandbox OOM kill was a sandbox resource constraint, not a code correctness issue.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
234 tool calls · 4 tool types · 264 steps
Agent session started, model: claude-opus-4-8 · 29 tools available · cwd: /app
I'll start by exploring the structure of the task and understanding what's 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 23:00 .
drwxr-xr-x 21 root root  4096 Jun 30 23:00 ..
-rw-r--r--  1 user user 14914 Jun 30 23:00 PROMPT.txt
-rw-r--r--  1 user user     5 Jun 30 23:00 agent.pid
-rw-r--r--  1 user user     0 Jun 30 23:00 agent.stderr
-rw-r--r--  1 user user  4498 Jun 30 23:00 agent_trajectory.jsonl
drwxr-xr-x  2 user user    60 Jun 30 23:00 data
-rw-r--r--  1 user user     0 Jun 30 23:00 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 23:00 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 23:00 .
drwxr-xr-x 4 user user  4096 Jun 30 23:00 ..
drwxr-xr-x 2 user user  4096 Jun 30 23:00 __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 23:00 .
drwxr-xr-x 4 user user    4096 Jun 30 23:00 ..
-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

/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]

/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]
Now let me look at the run_checks.py to understand exactly what's being tested.

/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]
Now I have a clear picture. Let me check the data and test.sh.

Inspect data shapes and groups

shell
cat test.sh && echo "---" && OMP_NUM_THREADS=1 python3 -c "
import numpy as np
d=np.load('data/train.npz'); print('train', {k:d[k].shape for k in d.files}, 'y range', d['y'].min(), d['y'].max(), 'g range', d['g'].min(), d['g'].max())
import collections
print('train group counts', collections.Counter(zip(d['y'].tolist(),d['g'].tolist())))
r=np.load('data/reweight.npz'); print('reweight', {k:r[k].shape for k in r.files})
print('reweight group counts', collections.Counter(zip(r['y'].tolist(),r['g'].tolist())))
"
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)"
---
train {'X': (2400, 3, 16, 16), 'y': (2400,), 'g': (2400,)} y range 0 3 g range 0 3
train group counts Counter({(2, 2): 586, (0, 0): 585, (1, 1): 580, (3, 3): 576, (1, 3): 11, (3,
…[truncated 405 chars]
I now understand the full task. Let me start implementing. First, add a helper and the `backward` method in autograd.py.

/app/submission/autograd.py

− removed
    while grad.ndim > len(shape):
        grad = grad.sum(axis=0)
    for ax, sz in enumerate(shape):
        if sz == 1 and grad.shape[ax] != 1:
            grad = grad.sum(axis=ax, keepdims=True)
    return grad.reshape(shape)
+ added
    while grad.ndim > len(shape):
        grad = grad.sum(axis=0)
    for ax, sz in enumerate(shape):
        if sz == 1 and grad.shape[ax] != 1:
            grad = grad.sum(axis=ax, keepdims=True)
    return grad.reshape(shape)


def _expand(g, shape, axis, keepdims):
    """Expand a reduced gradient ``g`` back to ``shape`` over ``axis`` (the backward of a
    sum/mean-style reduction)."""
    g = np.asarray(g, dtype=np.float64)
    if axis is None:
        return np.broadcast_to(g, shape).copy()
    axes = (axis,) if isinstance(axis, int) else tuple(axis)
    axes = tuple(ax % len(shape) for ax in axes)
    if not keepdims:
        ks = list(shape)
        for ax in axes:
            ks[ax] = 1
        g = g.reshape(ks)
    return np.broadcast_to(g, shape).copy()

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 = []
        visited = set()

        def build(t):
            if id(t) in visited:
                return
            visited.add(id(t))
            for p in t._parents:
                build(p)
            topo.append(t)
        build(self)
        if grad is None:
            grad = np.ones_like(self.data)
        else:
            grad = _as_f64(grad)
        if self.grad is None:
            self.grad = np.zeros_like(self.data)
        self.grad += 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 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
        ga = np.where(a.data > b.data, 1.0, np.where(a.data == b.data, 0.5, 0.0))
        if a.requires_grad:
            a._accum(_unbroadcast(g * ga, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * (1.0 - ga), 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
        ga = np.where(a.data < b.data, 1.0, np.where(a.data == b.data, 0.5, 0.0))
        if a.requires_grad:
            a._accum(_unbroadcast(g * ga, a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(g * (1.0 - ga), 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
        if a.requires_grad:
            a._accum(_unbroadcast(np.where(c, g, 0.0), a.data.shape))
        if b.requires_grad:
            b._accum(_unbroadcast(np.where(c, 0.0, 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 unary math:

/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:
            mm = a.data.max(axis=axis, keepdims=True)
            mask = (a.data == mm).astype(np.float64)
            counts = mask.sum(axis=axis, keepdims=True)
            g = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(mask * g / 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:
            mm = a.data.min(axis=axis, keepdims=True)
            mask = (a.data == mm).astype(np.float64)
            counts = mask.sum(axis=axis, keepdims=True)
            g = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(mask * g / 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, tuple(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
        idx = 0
        for t, sz in zip(ts, sizes):
            sl = [slice(None)] * g.ndim
            sl[axis] = slice(idx, idx + sz)
            if t.requires_grad:
                t._accum(g[tuple(sl)])
            idx += 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):
            sl = [slice(None)] * g.ndim
            sl[axis] = i
            if t.requires_grad:
                t._accum(g[tuple(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("matmul backward")  # TODO
+ added
        g = out.grad
        A = a.data
        B = b.data
        if a.requires_grad:
            da = g @ np.swapaxes(B, -1, -2)
            a._accum(_unbroadcast(da, A.shape))
        if b.requires_grad:
            db = np.swapaxes(A, -1, -2) @ g
            b._accum(_unbroadcast(db, B.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 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
            a._accum(s * (g - (g * s).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)

/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:

/app/submission/autograd.py

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

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:
            g = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(g * 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:
            g = _expand(out.grad, a.data.shape, axis, keepdims)
            a._accum(g * (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
            a._accum(np.flip(np.cumsum(np.flip(g, axis=axis), axis=axis), 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)
Now the generic 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)
Now the robustness losses:

/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[:, None] / wsum) * 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
            dfdp = g * (1.0 - p) ** (g - 1.0) * np.log(pc) - (1.0 - p) ** g / pc
            coef = dfdp * 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)
            term = (sm - y) + sm * (x - sx)
            logits._accum(2.0 * grad_w * (1.0 / n) * term * 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("gce_loss backward")  # TODO
+ added
        if logits.requires_grad:
            y = np.zeros_like(sm)
            y[np.arange(n), t] = 1.0
            logits._accum(-(pc ** qf)[:, 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:
            grad = (2.0 / K) * (r.data - mu) * out.grad
            r._accum(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)
Now normalization backwards (layernorm, batchnorm, batchnorm2d, rms_norm, groupnorm2d):

/app/submission/autograd.py

− removed
        raise NotImplementedError("layernorm backward")  # TODO
+ added
        g = out.grad
        gy = g * gamma.data
        mean_gy = gy.mean(axis=-1, keepdims=True)
        mean_gyxhat = (gy * xhat).mean(axis=-1, keepdims=True)
        if a.requires_grad:
            a._accum(inv * (gy - mean_gy - xhat * mean_gyxhat))
        axes = tuple(range(g.ndim - 1))
        if gamma.requires_grad:
            gamma._accum((g * xhat).sum(axis=axes))
        if beta.requires_grad:
            beta._accum(g.sum(axis=axes))

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
        gy = g * gamma.data
        mean_gy = gy.mean(axis=0, keepdims=True)
        mean_gyxhat = (gy * xhat).mean(axis=0, keepdims=True)
        if a.requires_grad:
            a._accum(inv * (gy - mean_gy - xhat * mean_gyxhat))
        if gamma.requires_grad:
            gamma._accum((g * xhat).sum(axis=0))
        if beta.requires_grad:
            beta._accum(g.sum(axis=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("batchnorm2d backward")  # TODO
+ added
        g = out.grad
        gy = g * gamma.data.reshape(1, C, 1, 1)
        if x.requires_grad:
            if training:
                sum_gy = gy.sum(axis=(0, 2, 3), keepdims=True)
                sum_gyxhat = (gy * xhat).sum(axis=(0, 2, 3), keepdims=True)
                dx = inv * (gy - sum_gy / m - xhat * sum_gyxhat / m)
            else:
                dx = gy * inv
            x._accum(dx)
        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)))

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
        gy = g * gamma.data
        ssum = (gy * x).sum(axis=-1, keepdims=True)
        if a.requires_grad:
            a._accum(r * gy - (r ** 3 / D) * x * ssum)
        axes = tuple(range(g.ndim - 1))
        if gamma.requires_grad:
            gamma._accum((g * xhat).sum(axis=axes))

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
        gg = g * g_
        gy = gg.reshape(N, G, cg * H * W)
        xhat_g = xhat.reshape(N, G, cg * H * W)
        mean_gy = gy.mean(axis=2, keepdims=True)
        mean_gyxhat = (gy * xhat_g).mean(axis=2, keepdims=True)
        if x.requires_grad:
            dx_g = inv * (gy - mean_gy - xhat_g * mean_gyxhat)
            x._accum(dx_g.reshape(N, C, H, W))
        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)))

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 add `_col2im` helper after `_im2col`, then conv2d backward:

/app/submission/autograd.py

− removed
    return cols.reshape(N, C * kh * kw, OH * OW), OH, OW
+ added
    return cols.reshape(N, C * kh * kw, OH * OW), OH, OW


def _col2im(cols, x_shape, kh, kw, pad, stride, OH, OW):
    """Inverse of ``_im2col``: scatter-add the column gradients back to the (strided, padded)
    input positions, then unpad."""
    N, C, H, W = x_shape
    Hp = H + 2 * pad
    Wp = W + 2 * pad
    xp = np.zeros((N, C, Hp, Wp), dtype=np.float64)
    cols = cols.reshape(N, C, kh, kw, OH, OW)
    for i in range(kh):
        for j in range(kw):
            xp[:, :, i:i + stride * OH:stride, j:j + stride * OW:stride] += cols[:, :, i, j]
    if pad:
        return xp[:, :, pad:pad + H, pad:pad + W]
    return xp

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("conv2d backward")  # TODO
+ added
        go = out.grad.reshape(N, Cout, OH * OW)
        if bias.requires_grad:
            bias._accum(out.grad.sum(axis=(0, 2, 3)))
        if weight.requires_grad:
            dWm = np.einsum("nop,nkp->ok", go, cols)
            weight._accum(dWm.reshape(Cout, Cin, kh, kw))
        if x.requires_grad:
            dcols = np.einsum("ok,nop->nkp", Wm, go)
            dx = _col2im(dcols, x.data.shape, kh, kw, pad, st, OH, OW)
            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)
Now the pools:

/app/submission/autograd.py

− removed
        raise NotImplementedError("maxpool2d backward")  # TODO
+ added
        if x.requires_grad:
            g = out.grad
            m = outd[:, :, :, None, :, None]
            mask = (xr == m).astype(np.float64)
            counts = mask.sum(axis=(3, 5), keepdims=True)
            gg = g[:, :, :, None, :, None] / counts
            dx = (mask * gg).reshape(N, C, H, W)
            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_stride backward")  # TODO
+ added
        if x.requires_grad:
            g = out.grad
            m = outd[:, :, None, None, :, :]
            mask = (win == m).astype(np.float64)
            counts = mask.sum(axis=(2, 3), keepdims=True)
            contrib = mask * (g[:, :, None, None, :, :] / counts)
            dxp = np.zeros((N, C, Hp, Wp), dtype=np.float64)
            for i in range(k):
                for j in range(k):
                    dxp[:, :, i:i + st * OH:st, j:j + st * OW:st] += contrib[:, :, i, j]
            if pad:
                dx = dxp[:, :, pad:pad + H, pad:pad + W]
            else:
                dx = 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:
            g = out.grad
            dx = np.empty((N, C, H // k, k, W // k, k), dtype=np.float64)
            dx[...] = g[:, :, :, None, :, None] / (k * k)
            x._accum(dx.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:
            g = out.grad
            dx = np.broadcast_to(g[:, :, None, None] / (H * W), (N, C, H, W)).copy()
            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("embedding backward")  # TODO
+ added
        if weight.requires_grad:
            ga = np.zeros_like(weight.data)
            np.add.at(ga, idx, out.grad)
            weight._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)
Now the two dropout backwards:

/app/submission/autograd.py

− removed
        def _bw_id():
            raise NotImplementedError("dropout backward")  # TODO
+ added
        def _bw_id():
            if a.requires_grad:
                a._accum(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("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)
Let me verify no remaining stubs in autograd.py and run the autograd checks:

Check remaining stubs in autograd

shell
grep -n "NotImplementedError" submission/autograd.py; echo "---count---"; grep -c "NotImplementedError" submission/autograd.py
output
3:YOU MUST IMPLEMENT EVERYTHING MARKED ``# TODO`` / ``raise NotImplementedError`` using numpy
---count---
1
autograd.py done. Now let me fill in 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 ResidualConvNet.forward:

/app/submission/nn.py

− removed
        # 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
        h = ag.silu(self.gn0(self.stem(X)))
        r = h
        h = ag.silu(self.b1n1(self.b1c1(h)))
        h = self.b1n2(self.b1c2(h))
        h = ag.silu(ag.add(h, r))
        r = h
        h = ag.silu(self.b2n1(self.b2c1(h)))
        h = self.b2n2(self.b2c2(h))
        h = ag.silu(ag.add(h, r))
        h = ag.silu(ag.conv2d(h, self.down.weight, self.down.bias, pad=1, stride=2))
        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)
Now SmallCNN featurize and forward:

/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:
        return self.classifier(self.featurize(X, training=training))

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 MLP, ResidualMLP, TinyConvNet forwards:

/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
        for i, lin in enumerate(self.layers):
            h = lin(h)
            if i < len(self.layers) - 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:
            n = blk["ln"](h)
            f = blk["fc2"](ag.gelu(blk["fc1"](n)))
            h = ag.add(h, f)
        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, 2 * self.W * 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 machinery helpers:

/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)
    K = len(present)
    w = np.zeros(int(n_groups), dtype=np.float64)
    w[present] = 1.0 / K
    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.maximum(counts, 1.0), 0.0)
    else:
        eff = (1.0 - beta ** counts) / (1.0 - beta)
        cw = np.where(counts > 0, 1.0 / np.maximum(eff, 1e-12), 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 = t.size
    prior = counts / N
    lp = np.where(counts > 0, np.log(np.maximum(prior, eps)), np.log(eps))
    return lp

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)
    m = np.where(counts > 0, np.maximum(counts, 1.0) ** (-0.25), 0.0)
    mx = m.max()
    if mx > 0:
        m = m / mx * max_margin
    return m

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)
    eff = (1.0 - beta ** counts) / (1.0 - beta)
    w = np.where(counts > 0, 1.0 / np.maximum(eff, 1e-12), 0.0)
    present = counts > 0
    w[present] = w[present] / 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)
Now EMAGroupLoss and GroupDROState:

/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):
        gl = np.asarray(group_losses, dtype=np.float64).reshape(-1)
        if present is None:
            present = np.ones(self.n_groups, dtype=bool)
        else:
            present = np.asarray(present, dtype=bool).reshape(-1)
        for k in range(self.n_groups):
            if not present[k]:
                continue
            if not self._init[k]:
                self.l[k] = gl[k]
                self._init[k] = True
            else:
                self.l[k] = self.beta * self.l[k] + (1.0 - self.beta) * gl[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):
        gl = np.asarray(group_losses, dtype=np.float64).reshape(-1)
        self.q = self.q * np.exp(self.eta_q * gl)
        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)

Check remaining stubs in nn.py

shell
grep -n "NotImplementedError\|# TODO" submission/nn.py
output
3:Implement every ``# TODO`` forward (and the robustness-helper bodies). The parameters +
44:        raise NotImplementedError
nn.py done (line 44 is the abstract base). Now 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] += 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] + (1.0 - 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
        b1, b2 = self.b1, self.b2
        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] + (1.0 - b1) * g
            self._v[i] = b2 * self._v[i] + (1.0 - b2) * (g * g)
            mhat = self._m[i] / (1.0 - b1 ** self.t)
            vhat = self._v[i] / (1.0 - b2 ** self.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
        b1, b2 = self.b1, self.b2
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            self._m[i] = b1 * self._m[i] + (1.0 - b1) * g
            self._v[i] = b2 * self._v[i] + (1.0 - b2) * (g * g)
            mhat = self._m[i] / (1.0 - b1 ** self.t)
            vhat = self._v[i] / (1.0 - b2 ** self.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
        b1, b2 = self.b1, self.b2
        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] + (1.0 - b1) * g
            self._u[i] = np.maximum(b2 * self._u[i], np.abs(g))
            p.data -= (self.lr / (1.0 - b1 ** self.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
        b1, b2 = self.b1, self.b2
        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] + (1.0 - b1) * g
            self._v[i] = b2 * self._v[i] + (1.0 - b2) * (g * g)
            mhat = self._m[i] / (1.0 - b1 ** self.t)
            vhat = self._v[i] / (1.0 - b2 ** self.t)
            mnes = b1 * mhat + (1.0 - b1) * g / (1.0 - b1 ** self.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
        b1, b2 = self.b1, self.b2
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            upd = np.sign(b1 * self._m[i] + (1.0 - b1) * g)
            p.data -= self.lr * (upd + self.weight_decay * p.data)
            self._m[i] = b2 * self._m[i] + (1.0 - 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)

/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
        b1, b2 = self.b1, self.b2
        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] = b1 * self._m[i] + (1.0 - b1) * g
            self._v[i] = b2 * self._v[i] + (1.0 - b2) * (g * g)
            bc2 = 1.0 - b2 ** t
            mhat = self._m[i] / (1.0 - b1 ** t)
            rinf = 2.0 / (1.0 - b2) - 1.0
            rt = rinf - 2.0 * t * (b2 ** t) / bc2
            if rt > 4.0:
                l = np.sqrt(bc2 / (self._v[i] + self.eps))
                r = math.sqrt(((rt - 4.0) * (rt - 2.0) * rinf) /
                              ((rinf - 4.0) * (rinf - 2.0) * 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
        b1, b2 = self.b1, self.b2
        for i, p in enumerate(self.params):
            if p.grad is None:
                continue
            g = p.grad
            self._m[i] = b1 * self._m[i] + (1.0 - b1) * g
            d = g - self._m[i]
            self._s[i] = b2 * self._s[i] + (1.0 - b2) * (d * d) + self.eps
            mhat = self._m[i] / (1.0 - b1 ** self.t)
            shat = self._s[i] / (1.0 - b2 ** self.t)
            p.data -= self.lr * (mhat / (np.sqrt(shat) + 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)
Now grad clipping and schedulers:

/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 *= 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:
            np.clip(p.grad, -clip_value, clip_value, out=p.grad)

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_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) * (1.0 + 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
    if step < warmup:
        return base_lr * (step + 1) / warmup
    return 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) * ((1.0 - 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) * (1.0 + 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)
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).astype(np.int64) * n_classes + np.asarray(g).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."""
    n = X.shape[0]
    perm = rng.permutation(n)
    for start in range(0, n, batch_size):
        idx = perm[start:start + 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)
    gid = group_ids(y, g, n_classes)
    correct = (preds == y).astype(np.float64)
    avg = float(correct.mean())
    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
    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 = group_ids(y, g, n_classes)
    mask = np.zeros(len(y), dtype=bool)
    for k in np.unique(gid):
        idx = np.where(gid == k)[0]
        rng.shuffle(idx)
        nsel = int(round(frac * len(idx)))
        nsel = max(0, min(len(idx), nsel))
        mask[idx[:nsel]] = 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 checks:

Run all public checks quiet

shell
OMP_NUM_THREADS=1 python3 run_checks.py --quiet 2>&1 | tail -20
output
----------------------------------------------------------------------
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.
All 147 public checks pass. Now let me write the training recipe. First let me write `train.py`:
write · /app/submission/train.py
"""Training entry point: worst-group-robust SmallCNN via ERM extractor + DFR last-layer retrain.

Recipe:
  1. Train the full SmallCNN on the correlated train split (ERM) -> good general features +
     batchnorm running buffers.
  2. (optional) Fine-tune the full model on the group-balanced reweight split so the conv
     features encode the SHAPE (the only predictor on balanced data).
  3. DFR: freeze the extractor and re-fit ONLY the classifier on the balanced reweight split with
     a group-weighted (balanced-group) loss so the head stops keying off background color.

Writes /app/submission/model.npz via save_checkpoint.
"""
from __future__ import annotations

import argparse
import json
import os
import sys

os.environ.setdefault("OMP_NUM_THREADS", "1")
os.environ.setdefault("OPENBLAS_NUM_THREADS", "1")
os.environ.setdefault("MKL_NUM_THREADS", "1")

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
import data as D               # noqa: E402,F401
import optim as O              # noqa: E402,F401
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 stat
…[truncated 5425 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 timing test of one ERM epoch before the full run:

Time one ERM epoch

shell
OMP_NUM_THREADS=1 python3 -c "
import time, numpy as np, sys
sys.path.insert(0,'submission')
import data as D, optim as O, autograd as ag
from nn import SmallCNN
Xtr,ytr,gtr=D.load_npz('data/train.npz')
m=SmallCNN(n_classes=4,img_size=16,width=16,embed_dim=48,seed=0)
params=m.params(); opt=O.AdamW(params,lr=2e-3,weight_decay=1e-4)
t0=time.time()
bs=128; rng=np.random.default_rng(0); perm=rng.permutation(len(ytr))
for s in range(0,len(ytr),bs):
    idx=perm[s:s+bs]; opt.zero_grad()
    loss=ag.cross_entropy(m(Xtr[idx],training=True),ytr[idx]); loss.backward()
    O.clip_grad_norm(params,5.0); opt.step()
print('1 epoch sec', round(time.time()-t0,2), 'last loss', round(float(loss.data),3))
" 2>&1 | tail -5
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 = 0.91  >= 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_59f774a8be4e4983. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_59f774a8be4e4983 · verifier authoritative; classifier explanatory.