SyncVals · Trajectory

lru-cache

claude-code claude-haiku-4-5 ✓ resolved GOOD_SUCCESS 17 turns · 54 tok in · 15,147 tok out ↑ 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

EvidenceAll 13 tests passed: test_output_exists, test_shipped_input_correct, test_shipped_exercises_the_gate, test_shipped_invariants, and test_hidden_inputs[3,4,8,11,13,16,33,47], plus test_hidden_inputs_are_nontrivial. Agent's output exactly matches reference implementation: get_results=[100,200,100,300,100,200,-1,400,100,200,-1,800,-1], final_probation=[[2,200]], final_protected=[[1,150],[8,800]], total_weight=5, rejected=2. Reference implementation in tests validates correctness independently.

Root causeAgent successfully implemented a complex two-segment LRU cache with all required features: logical clock expiration, frequency-gated admission, demotion-on-overflow, and periodic frequency halving. Implementation correctly handles reads (promotion), writes (updates with eviction, new admissions with frequency gating), and produces output matching the reference solution across all test cases including 8 hidden randomized traces.

RecommendationN/A - task is fine

Trajectory

Tool-by-tool agent trajectory

16 tool calls · 4 tool types · 29 steps

Looking at this cache simulation, I need to carefully implement a two-segment LRU cache with expiration, frequency-gated admission, and weight-based capacity. Let me build this step by step.

<tmp>/workspace

contents

EISDIR: illegal operation on a directory, read '<tmp>/workspace'

Let me check what's in the workspace directory.

shell

ls -la <tmp>/workspace/

output

total 40
drwxr-xr-x  7 jaykumar  staff   224 17 Jun 15:26 .
drwx------  4 jaykumar  staff   128 17 Jun 15:26 ..
drwxr-xr-x  3 jaykumar  staff    96 17 Jun 14:36 data
drwxr-xr-x  3 jaykumar  staff    96 17 Jun 14:36 environment
-rw-r--r--  1 jaykumar  staff  9746 17 Jun 14:36 instruction.md
-rw-r--r--  1 jaykumar  staff  1049 17 Jun 14:36 main.py
-rw-r--r--  1 jaykumar  staff   323 17 Jun 14:36 task.toml

Now let me read the trace data and the current stub.

<tmp>/workspace/data/operations.json

contents

1	{
2	  "capacity": 9,
3	  "protected_capacity": 4,
4	  "default_ttl": 8,
5	  "miss": -1,
6	  "reset_interval": 7,
7	  "operations": [
8	    ["put", 1, 100, 2],
9	    ["put", 2, 200, 2],
10	    ["put", 3, 300, 1],
11	    ["get", 1],
12	    ["get", 2],
13	    ["get", 1],
14	    ["put", 4, 400, 2],
15	    ["get", 3],
16	    ["get", 1],
17	    ["put", 5, 500, 2],
18	    ["get", 2],
19	    ["get", 99],
20	    ["put", 6, 600, 3],
21	    ["get", 4],
22	    ["put", 7, 700, 4],
23	    ["get", 1],
24	    ["get", 2],
25	    ["put", 8, 800, 1],
26	    ["get", 3],
27	    ["put", 1, 150, 2],
28	    ["get", 8],
29	    ["get", 77]
30	  ]
31	}
32

<tmp>/workspace/main.py

contents

1	# Read data/operations.json and write output/result.json.
2	#
3	# The input object carries: capacity, protected_capacity, default_ttl, miss,
4	# reset_interval, and operations (a list of ["put", key, value, cost] or
5	# ["get", key] entries).
6	#
7	# The output object must carry: get_results, final_probation, final_protected,
8	# total_weight, and rejected. See the task instructions for the exact rules
9	# (segmented recency, logical-clock expiry, weight budget, frequency-gated
10	# admission, demotion-on-overflow, and periodic frequency halving).
11	#
12	# TODO: implement the cache. The stub below writes an empty, incorrect result
13	# so that an unmodified program does not pass.
14	import json
15	import os
16	
17	with open("data/operations.json") as f:
18	    data = json.load(f)
19	
20	capacity = data["capacity"]
21	operations = data["operations"]
22	
23	result = {
24	    "get_results": [],
25	    "final_probation": [],
26	    "final_protected": [],
27	    "total_weight": 0,
28	    "rejected": 0,
29	}
30	
31	os.makedirs("output", exist_ok=True)
32	with open("output/result.json", "w") as f:
33	    json.dump(result, f)
34

Now I'll implement the full cache simulator following the rules precisely.

write · <tmp>/workspace/main.py

import json
import os

with open("data/operations.json") as f:
    data = json.load(f)

capacity = data["capacity"]
protected_capacity = data["protected_capacity"]
default_ttl = data["default_ttl"]
miss_value = data["miss"]
reset_interval = data["reset_interval"]
operations = data["operations"]

# Track entries in each segment: dict of key -> (value, cost, expiry_time)
probation = {}
protected = {}

# Frequency estimates for every key ever seen
frequency = {}

# Results
get_results = []
rejected_count = 0
operation_count = 0
clock = 0

def expire_entries():
    """Remove expired entries from both segments."""
    global probation, protected
    probation = {k: v for k, v in probation.items() if v[2] > clock}
    protected = {k: v for k, v in protected.items() if v[2] > clock}

def get_segment_weight(segment):
    """Calculate total weight of a segment."""
    return sum(cost for _, cost, _ in segment.values())

def evict_to_make_room(needed_weight):
    """
    Evict entries until there is at least needed_weight free.
    Evicts from probation first (LRU), then from protected (LRU).
    Returns the list of evicted keys.
    """
    global probation, protected
    evicted = []
    freed = 0

    # First, collect all evictable entries in order (LRU probation, then LRU protected)
    candidates = []

    # Probation entries in LRU order (index 0 is least recently used)
    for key in probation.keys():
        candidates.append(('probation', key))

    # Protected entries in LRU order
    for key in protected.keys():
        candidates.append(('protected', key))

    # Evict until we have enough space
    for segment_name, key in candidates:
        if freed >= needed_weight:
            break
        if segment_name == 'probation':
            _, cost, _ = probation[key]
            del probation[key]
        else:
            _, cost, _ = protected[key]
            del protected[key]
        evicted.append(key)
        freed += cost

    return evicted

def demote_from_protected():
    """
    After promotion, if protected segment exceeds protected_capacity,
    move LRU entries from protected back to probation (as most recently used).
    """
    global probation, protected

    while get_segment_weight(protected) > protected_capacity:
        # Find LRU entry in protected segment
        lru_key = next(iter(protected))
        value, cost, expiry = protected.pop(lru_key)
        probation[lru_key] = (value, cost, expiry)

def age_frequencies():
    """Halve all frequency estimates."""
    global frequency
    for key in frequency:
        frequency[key] //= 2

def handle_get(key):
    """Process a read operation."""
    global get_results, probation, protected, frequency, clock

    # Increment frequency
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1

    # Check if key is in protected segment
    if key in protected:
        value, cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        # Move to end (most recently used)
        protected.move_to_end(key)
        get_results.append(value)
        return

    # Check if key is in probation segment
    if key in probation:
        value, cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        # Promote to protected
        del probation[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)

        # Handle demotion if protected segment overflows
        demote_from_protected()

        get_results.append(value)
        return

    # Key not found
    get_results.append(miss_value)

def handle_put(key, value, cost):
    """Process a write operation."""
    global get_results, probation, protected, frequency, clock, rejected_count

    # Increment frequency
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1

    # If new entry's cost exceeds total capacity, refuse it
    if cost > capacity:
        rejected_count += 1
        return

    # If key already exists as a live entry, update it
    if key in protected:
        _, old_cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)

        # If weight increased, evict to make room
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return

    if key in probation:
        _, old_cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)

        # If weight increased, evict to make room
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return

    # Brand new entry: apply frequency gate
    current_free = capacity - (get_segment_weight(probation) + get_segment_weight(protected))

    if cost <= current_free:
        # No eviction needed
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)
        return

    # Need to evict some entries
    needed_weight = cost - current_free

    # Collect candidates in eviction order
    candidates = []
    for k in probation.keys():
        candidates.append((k, 'probation'))
    for k in protected.keys():
        candidates.append((k, 'protected'))

    # Walk candidates and check frequency gate
    accumulated_freed = 0
    entries_to_evict = []

    for candidate_key, segment_name in candidates:
        if segment_name == 'probation':
            _, candidate_cost, _ = probation[candidate_key]
        else:
            _, ca
… (+2019 chars truncated)

Now let me test it:

shell

python main.py

output

Exit code 127
(eval):1: command not found: python

shell

python3 <tmp>/workspace/main.py

output

Exit code 1
Traceback (most recent call last):
  File "<tmp>/workspace/main.py", line 242, in <module>
    handle_put(key, value, cost)
  File "<tmp>/workspace/main.py", line 177, in handle_put
    probation.move_to_end(key)
    ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'move_to_end'

I need to fix the import order issue. The OrderedDict initialization happens after it's used. Let me correct that:

<tmp>/workspace/main.py

− removed

import json
import os

with open("data/operations.json") as f:
    data = json.load(f)

+ added

import json
import os
from collections import OrderedDict

with open("data/operations.json") as f:
    data = json.load(f)

<tmp>/workspace/main.py

− removed

# Use OrderedDict for maintaining insertion order
from collections import OrderedDict
probation = OrderedDict()
protected = OrderedDict()

+ added

# OrderedDict already imported at top
probation = OrderedDict()
protected = OrderedDict()

shell

python3 main.py

output

Exit code 1
Traceback (most recent call last):
  File "<tmp>/workspace/main.py", line 242, in <module>
    handle_put(key, value, cost)
  File "<tmp>/workspace/main.py", line 178, in handle_put
    probation.move_to_end(key)
    ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'move_to_end'

The probation dict is being reinitialized as a plain dict. Let me check the issue more carefully:

<tmp>/workspace/main.py

contents

1	import json
2	import os
3	from collections import OrderedDict
4	
5	with open("data/operations.json") as f:
6	    data = json.load(f)
7	
8	capacity = data["capacity"]
9	protected_capacity = data["protected_capacity"]
10	default_ttl = data["default_ttl"]
11	miss_value = data["miss"]
12	reset_interval = data["reset_interval"]
13	operations = data["operations"]
14	
15	# Track entries in each segment: dict of key -> (value, cost, expiry_time)
16	probation = {}
17	protected = {}
18	
19	# Frequency estimates for every key ever seen
20	frequency = {}
21	
22	# Results
23	get_results = []
24	rejected_count = 0
25	operation_count = 0
26	clock = 0
27	
28	def expire_entries():
29	    """Remove expired entries from both segments."""
30	    global probation, protected
31	    probation = {k: v for k, v in probation.items() if v[2] > clock}
32	    protected = {k: v for k, v in protected.items() if v[2] > clock}
33	
34	def get_segment_weight(segment):
35	    """Calculate total weight of a segment."""
36	    return sum(cost for _, cost, _ in segment.values())
37	
38	def evict_to_make_room(needed_weight):
39	    """
40	    Evict entries until there is at least needed_weight free.

I see the issue - I initialize probation and protected as regular dicts at line 16-17, then try to reinitialize them later. The problem is that `expire_entries()` converts them to plain dicts. Let me rewrite this more carefully:

write · <tmp>/workspace/main.py

import json
import os
from collections import OrderedDict

with open("data/operations.json") as f:
    data = json.load(f)

capacity = data["capacity"]
protected_capacity = data["protected_capacity"]
default_ttl = data["default_ttl"]
miss_value = data["miss"]
reset_interval = data["reset_interval"]
operations = data["operations"]

# Track entries in each segment: OrderedDict of key -> (value, cost, expiry_time)
probation = OrderedDict()
protected = OrderedDict()

# Frequency estimates for every key ever seen
frequency = {}

# Results
get_results = []
rejected_count = 0
operation_count = 0
clock = 0

def expire_entries():
    """Remove expired entries from both segments."""
    global probation, protected
    # Keep only non-expired entries
    new_probation = OrderedDict()
    for k, v in probation.items():
        if v[2] > clock:
            new_probation[k] = v
    probation = new_probation

    new_protected = OrderedDict()
    for k, v in protected.items():
        if v[2] > clock:
            new_protected[k] = v
    protected = new_protected

def get_segment_weight(segment):
    """Calculate total weight of a segment."""
    return sum(cost for _, cost, _ in segment.values())

def evict_to_make_room(needed_weight):
    """
    Evict entries until there is at least needed_weight free.
    Evicts from probation first (LRU), then from protected (LRU).
    Returns the list of evicted keys.
    """
    global probation, protected
    evicted = []
    freed = 0

    # First, collect all evictable entries in order (LRU probation, then LRU protected)
    candidates = []

    # Probation entries in LRU order (index 0 is least recently used)
    for key in probation.keys():
        candidates.append(('probation', key))

    # Protected entries in LRU order
    for key in protected.keys():
        candidates.append(('protected', key))

    # Evict until we have enough space
    for segment_name, key in candidates:
        if freed >= needed_weight:
            break
        if segment_name == 'probation':
            _, cost, _ = probation[key]
            del probation[key]
        else:
            _, cost, _ = protected[key]
            del protected[key]
        evicted.append(key)
        freed += cost

    return evicted

def demote_from_protected():
    """
    After promotion, if protected segment exceeds protected_capacity,
    move LRU entries from protected back to probation (as most recently used).
    """
    global probation, protected

    while get_segment_weight(protected) > protected_capacity:
        # Find LRU entry in protected segment
        lru_key = next(iter(protected))
        value, cost, expiry = protected.pop(lru_key)
        probation[lru_key] = (value, cost, expiry)

def age_frequencies():
    """Halve all frequency estimates."""
    global frequency
    for key in frequency:
        frequency[key] //= 2

def handle_get(key):
    """Process a read operation."""
    global get_results, probation, protected, frequency, clock

    # Increment frequency
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1

    # Check if key is in protected segment
    if key in protected:
        value, cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        # Move to end (most recently used)
        protected.move_to_end(key)
        get_results.append(value)
        return

    # Check if key is in probation segment
    if key in probation:
        value, cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        # Promote to protected
        del probation[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)

        # Handle demotion if protected segment overflows
        demote_from_protected()

        get_results.append(value)
        return

    # Key not found
    get_results.append(miss_value)

def handle_put(key, value, cost):
    """Process a write operation."""
    global get_results, probation, protected, frequency, clock, rejected_count

    # Increment frequency
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1

    # If new entry's cost exceeds total capacity, refuse it
    if cost > capacity:
        rejected_count += 1
        return

    # If key already exists as a live entry, update it
    if key in protected:
        _, old_cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)

        # If weight increased, evict to make room
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return

    if key in probation:
        _, old_cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)

        # If weight increased, evict to make room
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return

    # Brand new entry: apply frequency gate
    current_free = capacity - (get_segment_weight(probation) + get_segment_weight(protected))

    if cost <= current_free:
        # No eviction needed
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)
        return

    # Need to evict some entries
    needed_weight = cost - current_free

    # Collect candidates in eviction order
    candidates = []
    for k in probation.keys():
        candidates.append((k, 'probation'))
    for k in protected.keys():
        candidates.append((k, 'protected'))

    
… (+2158 chars truncated)

shell

python3 main.py

output

{
  "get_results": [
    100,
    200,
    100,
    300,
    100,
    200,
    -1,
    400,
    100,
    200,
    -1,
    800,
    -1
  ],
  "final_probation": [
    [
      2,
      200
    ]
  ],
  "final_protected": [
    [
      1,
      150
    ],
    [
      8,
      800
    ]
  ],
  "total_weight": 5,
  "rejected": 2
}

Great! The program runs. Let me verify the output file was created:

shell

cat output/result.json

output

{"get_results": [100, 200, 100, 300, 100, 200, -1, 400, 100, 200, -1, 800, -1], "final_probation": [[2, 200]], "final_protected": [[1, 150], [8, 800]], "total_weight": 5, "rejected": 2}

Perfect! Let me trace through the execution to verify the logic is correct. Let me add some debug output to verify the cache behavior matches the rules:

shell

cat > /tmp/trace_cache.py << 'EOF'
import json
from collections import OrderedDict

with open("data/operations.json") as f:
    data = json.load(f)

capacity = data["capacity"]
protected_capacity = data["protected_capacity"]
default_ttl = data["default_ttl"]
miss_value = data["miss"]
reset_interval = data["reset_interval"]
operations = data["operations"]

probation = OrderedDict()
protected = OrderedDict()
frequency = {}
get_results = []
rejected_count = 0
operation_count = 0
clock = 0

def expire_entries():
    global probation, protected
    new_probation = OrderedDict()
    for k, v in probation.items():
        if v[2] > clock:
            new_probation[k] = v
    probation = new_probation
    new_protected = OrderedDict()
    for k, v in protected.items():
        if v[2] > clock:
            new_protected[k] = v
    protected = new_protected

def get_segment_weight(segment):
    return sum(cost for _, cost, _ in segment.values())

def evict_to_make_room(needed_weight):
    global probation, protected
    evicted = []
    freed = 0
    candidates = []
    for key in probation.keys():
        candidates.append(('probation', key))
    for key in protected.keys():
        candidates.append(('protected', key))
    for segment_name, key in candidates:
        if freed >= needed_weight:
            break
        if segment_name == 'probation':
            _, cost, _ = probation[key]
            del probation[key]
        else:
            _, cost, _ = protected[key]
            del protected[key]
        evicted.append(key)
        freed += cost
    return evicted

def demote_from_protected():
    global probation, protected
    while get_segment_weight(protected) > protected_capacity:
        lru_key = next(iter(protected))
        value, cost, expiry = protected.pop(lru_key)
        probation[lru_key] = (value, cost, expiry)

def age_frequencies():
    global frequency
    for key in frequency:
        frequency[key] //= 2

def handle_get(key):
    global get_results, probation, protected, frequency, clock
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1
    if key in protected:
        value, cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)
        get_results.append(value)
        return
    if key in probation:
        value, cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        del probation[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)
        demote_from_protected()
        get_results.append(value)
        return
    get_results.append(miss_value)

def handle_put(key, value, cost):
    global get_results, probation, protected, frequency, clock, rejected_count
    if key not in frequency:
        frequency[key] = 0
    frequency[key] += 1
    if cost > capacity:
        rejected_count += 1
        return
    if key in protected:
        _, old_cost, _ = protected[key]
        protected[key] = (value, cost, clock + default_ttl)
        protected.move_to_end(key)
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return
    if key in probation:
        _, old_cost, _ = probation[key]
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)
        weight_increase = cost - old_cost
        if weight_increase > 0:
            total_used = get_segment_weight(probation) + get_segment_weight(protected)
            if total_used > capacity:
                needed = total_used - capacity
                evict_to_make_room(needed)
        return
    current_free = capacity - (get_segment_weight(probation) + get_segment_weight(protected))
    if cost <= current_free:
        probation[key] = (value, cost, clock + default_ttl)
        probation.move_to_end(key)
        return
    needed_weight = cost - current_free
    candidates = []
    for k in probation.keys():
        candidates.append((k, 'probation'))
    for k in protected.keys():
        candidates.append((k, 'protected'))
    accumulated_freed = 0
    entries_to_evict = []
    for candidate_key, segment_name in candidates:
        if segment_name == 'probation':
            _, candidate_cost, _ = probation[candidate_key]
        else:
            _, candidate_cost, _ = protected[candidate_key]
        candidate_freq = frequency.get(candidate_key, 0)
        new_freq = frequency.get(key, 0)
        if candidate_freq >= new_freq:
            rejected_count += 1
            return
        entries_to_evict.append((candidate_key, segment_name, candidate_cost))
        accumulated_freed += candidate_cost
        if accumulated_freed >= needed_weight:
            break
    for candidate_key, segment_name, _ in entries_to_evict:
        if segment_name == 'probation':
            del probation[candidate_key]
        else:
            del protected[candidate_key]
    probation[key] = (value, cost, clock + default_ttl)
    probation.move_to_end(key)

for i, op in enumerate(operations):
    clock += 1
    print(f"\n=== Op {i+1} (clock={clock}): {op} ===")
    print(f"Before: probation={dict(probation)}, protected={dict(protected)}, freq={frequency}")
    
    expire_entries()
    print(f"After expiry: probation={dict(probation)}, protected={dict(protected)}")
    
    if op[0] == "get":
        key = op[1]
        handle_get(key)
    elif op[0] == "put":
        key, value, cost = op[1], op[2], op[3]
        handle_put(key, value, cost)
    
    print(f"After op: probation={dict(probation)}, protected={dict(protected)}, freq={frequency}")
    
    operation_count += 1
    if operation_count % reset_interval == 0:
        print(f"Aging frequencies!")
        age_frequencies(
… (+165 chars truncated)

output

=== Op 1 (clock=1): ['put', 1, 100, 2] ===
Before: probation={}, protected={}, freq={}
After expiry: probation={}, protected={}
After op: probation={1: (100, 2, 9)}, protected={}, freq={1: 1}

=== Op 2 (clock=2): ['put', 2, 200, 2] ===
Before: probation={1: (100, 2, 9)}, protected={}, freq={1: 1}
After expiry: probation={1: (100, 2, 9)}, protected={}
After op: probation={1: (100, 2, 9), 2: (200, 2, 10)}, protected={}, freq={1: 1, 2: 1}

=== Op 3 (clock=3): ['put', 3, 300, 1] ===
Before: probation={1: (100, 2, 9), 2: (200, 2, 10)}, protected={}, freq={1: 1, 2: 1}
After expiry: probation={1: (100, 2, 9), 2: (200, 2, 10)}, protected={}
After op: probation={1: (100, 2, 9), 2: (200, 2, 10), 3: (300, 1, 11)}, protected={}, freq={1: 1, 2: 1, 3: 1}

=== Op 4 (clock=4): ['get', 1] ===
Before: probation={1: (100, 2, 9), 2: (200, 2, 10), 3: (300, 1, 11)}, protected={}, freq={1: 1, 2: 1, 3: 1}
After expiry: probation={1: (100, 2, 9), 2: (200, 2, 10), 3: (300, 1, 11)}, protected={}
After op: probation={2: (200, 2, 10), 3: (300, 1, 11)}, protected={1: (100, 2, 12)}, freq={1: 2, 2: 1, 3: 1}

=== Op 5 (clock=5): ['get', 2] ===
Before: probation={2: (200, 2, 10), 3: (300, 1, 11)}, protected={1: (100, 2, 12)}, freq={1: 2, 2: 1, 3: 1}
After expiry: probation={2: (200, 2, 10), 3: (300, 1, 11)}, protected={1: (100, 2, 12)}
After op: probation={3: (300, 1, 11)}, protected={1: (100, 2, 12), 2: (200, 2, 13)}, freq={1: 2, 2: 2, 3: 1}

=== Op 6 (clock=6): ['get', 1] ===
Before: probation={3: (300, 1, 11)}, protected={1: (100, 2, 12), 2: (200, 2, 13)}, freq={1: 2, 2: 2, 3: 1}
After expiry: probation={3: (300, 1, 11)}, protected={1: (100, 2, 12), 2: (200, 2, 13)}
After op: probation={3: (300, 1, 11)}, protected={2: (200, 2, 13), 1: (100, 2, 14)}, freq={1: 3, 2: 2, 3: 1}

=== Op 7 (clock=7): ['put', 4, 400, 2] ===
Before: probation={3: (300, 1, 11)}, protected={2: (200, 2, 13), 1: (100, 2, 14)}, freq={1: 3, 2: 2, 3: 1}
After expiry: probation={3: (300, 1, 11)}, protected={2: (200, 2, 13), 1: (1
… (+7387 chars truncated)

Excellent! The trace looks correct. Let me verify the final result matches the expected output: - **get_results**: [100, 200, 100, 300, 100, 200, -1, 400, 100, 200, -1, 800, -1] ✓ - **final_probation**: [[2, 200]] - Key 2 with value 200 in probation ✓ - **final_protected**: [[1, 150], [8, 800]] - Key 1 with value 150 and key 8 with value 800 in protected ✓ - **total_weight**: 2 + 2 + 1 = 5 ✓ - **rejected**: 2 (operations for keys 6 and 7 were refused due to frequency gate) ✓ The cache simulation is working correctly! Let me verify the file was created with the correct format:

shell

python3 main.py && echo "---" && cat output/result.json

output

{
  "get_results": [
    100,
    200,
    100,
    300,
    100,
    200,
    -1,
    400,
    100,
    200,
    -1,
    800,
    -1
  ],
  "final_probation": [
    [
      2,
      200
    ]
  ],
  "final_protected": [
    [
      1,
      150
    ],
    [
      8,
      800
    ]
  ],
  "total_weight": 5,
  "rejected": 2
}
---
{"get_results": [100, 200, 100, 300, 100, 200, -1, 400, 100, 200, -1, 800, -1], "final_probation": [[2, 200]], "final_protected": [[1, 150], [8, 800]], "total_weight": 5, "rejected": 2}

Perfect! The implementation is complete and working correctly. The cache simulator: 1. ✓ Maintains a logical clock that advances before each operation 2. ✓ Expires entries when clock reaches/passes their expiry time 3. ✓ Tracks frequency estimates for every key with periodic halving 4. ✓ Keeps two segments: probation (new entries) and protected (entries proven useful via reads) 5. ✓ On reads: returns value from protected segment or promotes from probation with demotion handling 6. ✓ On writes: updates existing entries with potential evictions, or attempts to admit new entries with frequency gating 7. ✓ Uses LRU within each segment for eviction order 8. ✓ Properly implements the frequency gate for new admissions (new key must beat all entries to evict) 9. ✓ Produces correct JSON output with all five required fields The program reads `data/operations.json` and writes the result to `output/result.json` as requested.

Final diff , what the agent changed

--- a/main.py

+++ b/main.py

@@ -1,33 +1,273 @@

-# Read data/operations.json and write output/result.json.

-# The input object carries: capacity, protected_capacity, default_ttl, miss,

-# reset_interval, and operations (a list of ["put", key, value, cost] or

-# ["get", key] entries).

-# The output object must carry: get_results, final_probation, final_protected,

-# total_weight, and rejected. See the task instructions for the exact rules

-# (segmented recency, logical-clock expiry, weight budget, frequency-gated

-# admission, demotion-on-overflow, and periodic frequency halving).

-# TODO: implement the cache. The stub below writes an empty, incorrect result

-# so that an unmodified program does not pass.

import json

import os

+from collections import OrderedDict

with open("data/operations.json") as f:

data = json.load(f)

capacity = data["capacity"]

+protected_capacity = data["protected_capacity"]

+default_ttl = data["default_ttl"]

+miss_value = data["miss"]

+reset_interval = data["reset_interval"]

operations = data["operations"]

+# Track entries in each segment: OrderedDict of key -> (value, cost, expiry_time)

+probation = OrderedDict()

+protected = OrderedDict()

+# Frequency estimates for every key ever seen

+frequency = {}

+# Results

+get_results = []

+rejected_count = 0

+operation_count = 0

+clock = 0

+def expire_entries():

+ """Remove expired entries from both segments."""

+ global probation, protected

+ # Keep only non-expired entries

+ new_probation = OrderedDict()

+ for k, v in probation.items():

+ if v[2] > clock:

+ new_probation[k] = v

+ probation = new_probation

+ new_protected = OrderedDict()

+ for k, v in protected.items():

+ if v[2] > clock:

+ new_protected[k] = v

+ protected = new_protected

+def get_segment_weight(segment):

+ """Calculate total weight of a segment."""

+ return sum(cost for _, cost, _ in segment.values())

+def evict_to_make_room(needed_weight):

+ """

+ Evict entries until there is at least needed_weight free.

+ Evicts from probation first (LRU), then from protected (LRU).

+ Returns the list of evicted keys.

+ """

+ global probation, protected

+ evicted = []

+ freed = 0

+ # First, collect all evictable entries in order (LRU probation, then LRU protected)

+ candidates = []

+ # Probation entries in LRU order (index 0 is least recently used)

+ for key in probation.keys():

+ candidates.append(('probation', key))

+ # Protected entries in LRU order

+ for key in protected.keys():

+ candidates.append(('protected', key))

+ # Evict until we have enough space

+ for segment_name, key in candidates:

+ if freed >= needed_weight:

+ break

+ if segment_name == 'probation':

+ _, cost, _ = probation[key]

+ del probation[key]

+ else:

+ _, cost, _ = protected[key]

+ del protected[key]

+ evicted.append(key)

+ freed += cost

+ return evicted

+def demote_from_protected():

+ """

+ After promotion, if protected segment exceeds protected_capacity,

+ move LRU entries from protected back to probation (as most recently used).

+ """

+ global probation, protected

+ while get_segment_weight(protected) > protected_capacity:

+ # Find LRU entry in protected segment

+ lru_key = next(iter(protected))

+ value, cost, expiry = protected.pop(lru_key)

+ probation[lru_key] = (value, cost, expiry)

+def age_frequencies():

+ """Halve all frequency estimates."""

+ global frequency

+ for key in frequency:

+ frequency[key] //= 2

+def handle_get(key):

+ """Process a read operation."""

+ global get_results, probation, protected, frequency, clock

+ # Increment frequency

+ if key not in frequency:

+ frequency[key] = 0

+ frequency[key] += 1

+ # Check if key is in protected segment

+ if key in protected:

+ value, cost, _ = protected[key]

+ protected[key] = (value, cost, clock + default_ttl)

+ # Move to end (most recently used)

+ protected.move_to_end(key)

+ get_results.append(value)

+ return

+ # Check if key is in probation segment

+ if key in probation:

+ value, cost, _ = probation[key]

+ probation[key] = (value, cost, clock + default_ttl)

+ # Promote to protected

+ del probation[key]

+ protected[key] = (value, cost, clock + default_ttl)

+ protected.move_to_end(key)

+ # Handle demotion if protected segment overflows

+ demote_from_protected()

+ get_results.append(value)

+ return

+ # Key not found

+ get_results.append(miss_value)

+def handle_put(key, value, cost):

+ """Process a write operation."""

+ global get_results, probation, protected, frequency, clock, rejected_count

+ # Increment frequency

+ if key not in frequency:

+ frequency[key] = 0

+ frequency[key] += 1

+ # If new entry's cost exceeds total capacity, refuse it

+ if cost > capacity:

+ rejected_count += 1

+ return

+ # If key already exists as a live entry, update it

+ if key in protected:

+ _, old_cost, _ = protected[key]

+ protected[key] = (value, cost, clock + default_ttl)

+ protected.move_to_end(key)

+ # If weight increased, evict to make room

+ weight_increase = cost - old_cost

+ if weight_increase > 0:

+ total_used = get_segment_weight(probation) + get_segment_weight(protected)

+ if total_used > capacity:

+ needed = total_used - capacity

+ evict_to_make_room(needed)

+ return

+ if key in probation:

+ _, old_cost, _ = probation[key]

+ probation[key] = (value, cost, clock + default_ttl)

+ probation.move_to_end(key)

+ # If weight increased, evict to make room

+ weight_increase = cost - old_cost

+ if weight_increase > 0:

+ total_used = get_segment_weight(probation) + get_segment_weight(protected)

+ if total_used > capacity:

+ needed = total_used - capacity

+ evict_to_make_room(needed)

+ return

+ # Brand new entry: apply frequency gate

+ current_free = capacity - (get_segment_weight(probation) + get_segment_weight(protected))

+ if cost <= current_free:

+ # No eviction needed

+ probation[key] = (value, cost, clock + default_ttl)

+ probation.move_to_end(key)

+ return

+ # Need to evict some entries

+ needed_weight = cost - current_free

+ # Collect candidates in eviction order

+ candidates = []

+ for k in probation.keys():

+ candidates.append((k, 'probation'))

+ for k in protected.keys():

+ candidates.append((k, 'protected'))

+ # Walk candidates and check frequency gate

+ accumulated_freed = 0

+ entries_to_evict = []

+ for candidate_key, segment_name in candidates:

+ if segment_name == 'probation':

+ _, candidate_cost, _ = probation[candidate_key]

+ else:

+ _, candidate_cost, _ = protected[candidate_key]

+ candidate_freq = frequency.get(candidate_key, 0)

+ new_freq = frequency.get(key, 0)

+ # If candidate's frequency is >= new key's frequency, gate fails

+ if candidate_freq >= new_freq:

+ rejected_count += 1

+ return

+ entries_to_evict.append((candidate_key, segment_name, candidate_cost))

+ accumulated_freed += candidate_cost

+ if accumulated_freed >= needed_weight:

+ break

+ # All candidates passed the gate; perform evictions

+ for candidate_key, segment_name, _ in entries_to_evict:

+ if segment_name == 'probation':

+ del probation[candidate_key]

+ else:

+ del protected[candidate_key]

+ # Insert new entry into probation

+ probation[key] = (value, cost, clock + default_ttl)

+ probation.move_to_end(key)

+# Process operations

+for op in operations:

+ clock += 1

+ # Expire entries

+ expire_entries()

+ if op[0] == "get":

+ key = op[1]

+ handle_get(key)

+ elif op[0] == "put":

+ key, value, cost = op[1], op[2], op[3]

+ handle_put(key, value, cost)

+ operation_count += 1

+ # Age frequencies if operation count is a multiple of reset_interval

+ if operation_count % reset_interval == 0:

+ age_frequencies()

+# Build final result

+final_probation = [[k, v[0]] for k, v in probation.items()]

+final_protected = [[k, v[0]] for k, v in protected.items()]

+total_weight = get_segment_weight(probation) + get_segment_weight(protected)

result = {

- "get_results": [],

- "final_probation": [],

- "final_protected": [],

- "total_weight": 0,

- "rejected": 0,

+ "get_results": get_results,

+ "final_probation": final_probation,

+ "final_protected": final_protected,

+ "total_weight": total_weight,

+ "rejected": rejected_count,

}

os.makedirs("output", exist_ok=True)

with open("output/result.json", "w") as f:

json.dump(result, f)

+print(json.dumps(result, indent=2))

--- /dev/null

+++ b/output/result.json

@@ -0,0 +1 @@

+{"get_results": [100, 200, 100, 300, 100, 200, -1, 400, 100, 200, -1, 800, -1], "final_probation": [[2, 200]], "final_protected": [[1, 150], [8, 800]], "total_weight": 5, "rejected": 2}

Verifier output , the proof behind the reward

tests/test.sh

{
  "get_results": [
    100,
    200,
    100,
    300,
    100,
    200,
    -1,
    400,
    100,
    200,
    -1,
    800,
    -1
  ],
  "final_probation": [
    [
      2,
      200
    ]
  ],
  "final_protected": [
    [
      1,
      150
    ],
    [
      8,
      800
    ]
  ],
  "total_weight": 5,
  "rejected": 2
}
============================= test session starts ==============================
platform darwin -- Python 3.12.4, pytest-8.4.1, pluggy-1.6.0 -- /Library/Frameworks/Python.framework/Versions/3.12/bin/python3
cachedir: .pytest_cache
rootdir: <tmp>/workspace
plugins: anyio-4.12.1, respx-0.22.0, mock-3.15.1, asyncio-0.21.1
asyncio: mode=Mode.STRICT
collecting ... collected 13 items

tests/test_outputs.py::test_output_exists PASSED                         [  7%]
tests/test_outputs.py::test_shipped_input_correct PASSED                 [ 15%]
tests/test_outputs.py::test_shipped_exercises_the_gate PASSED            [ 23%]
tests/test_outputs.py::test_shipped_invariants PASSED                    [ 30%]
tests/test_outputs.py::test_hidden_inputs[3] PASSED                      [ 38%]
tests/test_outputs.py::test_hidden_inputs[4] PASSED                      [ 46%]
tests/test_outputs.py::test_hidden_inputs[8] PASSED                      [ 53%]
tests/test_outputs.py::test_hidden_inputs[11] PASSED                     [ 61%]
tests/test_outputs.py::test_hidden_inputs[13] PASSED                     [ 69%]
tests/test_outputs.py::test_hidden_inputs[16] PASSED                     [ 76%]
tests/test_outputs.py::test_hidden_inputs[33] PASSED                     [ 84%]
tests/test_outputs.py::test_hidden_inputs[47] PASSED                     [ 92%]
tests/test_outputs.py::test_hidden_inputs_are_nontrivial PASSED          [100%]

============================== 13 passed in 0.33s ==============================

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_9a3fa7d9698a44de. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_9a3fa7d9698a44de · verifier authoritative; classifier explanatory.