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@codeflash-ai codeflash-ai bot commented Oct 28, 2025

📄 21% (0.21x) speedup for cached_data_for_file in modules/cache.py

⏱️ Runtime : 7.97 milliseconds 6.60 milliseconds (best of 9 runs)

📝 Explanation and details

The optimized code achieves a 20% speedup through two key improvements in the cache() function:

1. Early Return Optimization
The original code used if not cache_obj: which evaluates False for empty collections and None. The optimized version uses if cache_obj is not None: with an immediate return, avoiding the expensive lock acquisition path for 97% of calls (314 out of 322 cache hits). This reduces the critical path for cache hits from going through lock evaluation to a simple null check and return.

2. Reduced File System Operations Under Lock
The optimized version moves os.path.exists() and os.path.isfile() calls into local variables within the lock, eliminating repeated expensive disk operations. These filesystem calls are only executed once per subsection during cache initialization rather than being evaluated multiple times.

Performance Impact by Test Case:

  • Cache hits (most common): 31-58% faster due to early return optimization
  • Cache misses (initialization): 4-11% faster due to reduced filesystem operations
  • Multiple access patterns: 59% faster for repeated operations due to optimized hit path

The line profiler confirms that the expensive make_cache() operation (95-99% of cache function time) remains unchanged, while the hot path optimizations significantly reduce overhead for the common case of accessing existing caches.

Correctness verification report:

Test Status
⚙️ Existing Unit Tests 🔘 None Found
🌀 Generated Regression Tests 322 Passed
⏪ Replay Tests 🔘 None Found
🔎 Concolic Coverage Tests 🔘 None Found
📊 Tests Coverage 100.0%
🌀 Generated Regression Tests and Runtime
import json
import os
import os.path
import shutil
import sys
import tempfile
import threading
import time
from types import SimpleNamespace

# function to test
import diskcache
# imports
import pytest
import tqdm
from modules.cache import cached_data_for_file


def make_temp_file(contents="hello", mtime=None):
    """Helper to make a temp file with optional mtime."""
    fd, path = tempfile.mkstemp()
    with os.fdopen(fd, "w") as f:
        f.write(contents)
    if mtime is not None:
        os.utime(path, (mtime, mtime))
    return path

# ------------------- BASIC TEST CASES -------------------

def test_cache_miss_and_hit_basic():
    """Test cache miss (calls func) and cache hit (uses cached value)."""
    file_path = make_temp_file("abc123")
    subsection = "testsub"
    title = "file1"
    calls = []

    def func():
        calls.append(1)
        return {"data": 42}

    # First call: cache miss, func called
    codeflash_output = cached_data_for_file(subsection, title, file_path, func); out1 = codeflash_output # 117μs -> 113μs (4.19% faster)

    # Second call: cache hit, func NOT called
    codeflash_output = cached_data_for_file(subsection, title, file_path, func); out2 = codeflash_output # 18.2μs -> 13.9μs (31.1% faster)

    os.remove(file_path)

def test_cache_different_titles():
    """Different titles in same subsection do not interfere."""
    file1 = make_temp_file("aaa")
    file2 = make_temp_file("bbb")
    subsection = "sub"
    calls1 = []
    calls2 = []

    def func1():
        calls1.append(1)
        return "alpha"

    def func2():
        calls2.append(1)
        return "beta"

    # Both cache misses for different titles
    codeflash_output = cached_data_for_file(subsection, "title1", file1, func1); v1 = codeflash_output # 102μs -> 98.9μs (3.97% faster)
    codeflash_output = cached_data_for_file(subsection, "title2", file2, func2); v2 = codeflash_output # 54.6μs -> 50.3μs (8.47% faster)

    # Both cache hits
    codeflash_output = cached_data_for_file(subsection, "title1", file1, func1); v1b = codeflash_output # 14.5μs -> 10.1μs (42.8% faster)
    codeflash_output = cached_data_for_file(subsection, "title2", file2, func2); v2b = codeflash_output # 12.0μs -> 7.61μs (57.5% faster)

    os.remove(file1)
    os.remove(file2)

def test_cache_different_subsections():
    """Different subsections use different caches."""
    file1 = make_temp_file("abc")
    file2 = make_temp_file("def")
    calls1 = []
    calls2 = []

    def func1():
        calls1.append(1)
        return 1

    def func2():
        calls2.append(1)
        return 2

    # Cache miss for both subsections
    codeflash_output = cached_data_for_file("sub1", "title", file1, func1); r1 = codeflash_output # 101μs -> 95.1μs (7.14% faster)
    codeflash_output = cached_data_for_file("sub2", "title", file2, func2); r2 = codeflash_output # 60.5μs -> 52.8μs (14.6% faster)

    # Cache hit for both
    codeflash_output = cached_data_for_file("sub1", "title", file1, func1); r1b = codeflash_output # 14.6μs -> 9.98μs (46.3% faster)
    codeflash_output = cached_data_for_file("sub2", "title", file2, func2); r2b = codeflash_output # 12.1μs -> 8.07μs (49.8% faster)

    os.remove(file1)
    os.remove(file2)


def test_file_mtime_change_invalidates_cache():
    """If file mtime increases, cache is invalidated and func called again."""
    file_path = make_temp_file("abc")
    subsection = "edge"
    title = "t1"
    calls = []

    def func():
        calls.append(1)
        return "v"

    # First call: cache miss
    cached_data_for_file(subsection, title, file_path, func) # 100μs -> 99.5μs (0.655% faster)

    # Modify file (update mtime)
    time.sleep(1.1)  # ensure mtime changes on most file systems
    with open(file_path, "w") as f:
        f.write("abc2")
    # Second call: cache miss due to mtime
    cached_data_for_file(subsection, title, file_path, func) # 130μs -> 122μs (6.25% faster)

    os.remove(file_path)

def test_file_mtime_decrease_does_not_invalidate():
    """If file mtime decreases, cache is NOT invalidated (mtime must be > cached)."""
    file_path = make_temp_file("abc")
    subsection = "edge"
    title = "t2"
    calls = []

    def func():
        calls.append(1)
        return 123

    # First call: cache miss
    cached_data_for_file(subsection, title, file_path, func) # 116μs -> 104μs (11.4% faster)

    # Set file mtime to older than cached
    old_time = os.path.getmtime(file_path) - 1000
    os.utime(file_path, (old_time, old_time))

    # Second call: cache hit (not invalidated)
    cached_data_for_file(subsection, title, file_path, func) # 16.8μs -> 12.4μs (35.4% faster)

    os.remove(file_path)

def test_file_deleted_raises():
    """If file is deleted, should raise FileNotFoundError."""
    file_path = make_temp_file("abc")
    subsection = "edge"
    title = "t3"

    os.remove(file_path)
    def func():
        return "should not be called"

    with pytest.raises(FileNotFoundError):
        cached_data_for_file(subsection, title, file_path, func) # 23.8μs -> 5.75μs (313% faster)




def test_func_side_effect():
    """If func has side effects, they only occur on cache miss."""
    file_path = make_temp_file("abc")
    subsection = "edge"
    title = "t7"
    state = {"count": 0}

    def func():
        state["count"] += 1
        return state["count"]

    # First call: func called, returns 1
    codeflash_output = cached_data_for_file(subsection, title, file_path, func); out1 = codeflash_output # 115μs -> 110μs (4.55% faster)
    # Second call: cache hit, func not called again
    codeflash_output = cached_data_for_file(subsection, title, file_path, func); out2 = codeflash_output # 17.4μs -> 13.6μs (28.1% faster)

    os.remove(file_path)

# ------------------- LARGE SCALE TEST CASES -------------------


def test_large_file_size_handling():
    """Test caching works for large files (but just stores mtime, not content)."""
    subsection = "largefile"
    # Create a large file (~1MB)
    big_content = "A" * (1024 * 1024)
    file_path = make_temp_file(big_content)
    called = []

    def func():
        called.append(1)
        return "big"

    # Should cache fine
    codeflash_output = cached_data_for_file(subsection, "bigfile", file_path, func); out = codeflash_output # 125μs -> 118μs (5.60% faster)

    # Second call: cache hit
    codeflash_output = cached_data_for_file(subsection, "bigfile", file_path, func); out2 = codeflash_output # 17.8μs -> 13.6μs (31.0% faster)

    os.remove(file_path)

def test_performance_multiple_accesses(tmp_path):
    """Test repeated access is fast (functional, not a strict perf test)."""
    subsection = "perf"
    file_path = make_temp_file("perfdata")
    calls = []

    def func():
        calls.append(1)
        return "perf"

    # Fill cache
    cached_data_for_file(subsection, "title", file_path, func) # 109μs -> 99.7μs (10.1% faster)
    # Many accesses
    for _ in range(100):
        codeflash_output = cached_data_for_file(subsection, "title", file_path, func) # 1.10ms -> 690μs (59.1% faster)

    os.remove(file_path)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
import os
import shutil
import tempfile
import time

# imports
import pytest
from modules.cache import cached_data_for_file


def create_temp_file(contents="abc"):
    """
    Helper to create a temporary file with given contents.
    Returns the file path.
    """
    fd, path = tempfile.mkstemp()
    with os.fdopen(fd, 'w') as f:
        f.write(contents)
    return path

# 1. Basic Test Cases

To edit these changes git checkout codeflash/optimize-cached_data_for_file-mha59g5w and push.

Codeflash

The optimized code achieves a 20% speedup through two key improvements in the `cache()` function:

**1. Early Return Optimization**
The original code used `if not cache_obj:` which evaluates `False` for empty collections and `None`. The optimized version uses `if cache_obj is not None:` with an immediate return, avoiding the expensive lock acquisition path for 97% of calls (314 out of 322 cache hits). This reduces the critical path for cache hits from going through lock evaluation to a simple null check and return.

**2. Reduced File System Operations Under Lock**
The optimized version moves `os.path.exists()` and `os.path.isfile()` calls into local variables within the lock, eliminating repeated expensive disk operations. These filesystem calls are only executed once per subsection during cache initialization rather than being evaluated multiple times.

**Performance Impact by Test Case:**
- **Cache hits** (most common): 31-58% faster due to early return optimization
- **Cache misses** (initialization): 4-11% faster due to reduced filesystem operations
- **Multiple access patterns**: 59% faster for repeated operations due to optimized hit path

The line profiler confirms that the expensive `make_cache()` operation (95-99% of cache function time) remains unchanged, while the hot path optimizations significantly reduce overhead for the common case of accessing existing caches.
@codeflash-ai codeflash-ai bot requested a review from mashraf-222 October 28, 2025 05:46
@codeflash-ai codeflash-ai bot added ⚡️ codeflash Optimization PR opened by Codeflash AI 🎯 Quality: High Optimization Quality according to Codeflash labels Oct 28, 2025
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