⚡️ Speed up function generate_candidates by 1,729% in PR #363 (part-1-windows-fixes)

[codeflash-ai]

⚡️ This pull request contains optimizations for PR #363

If you approve this dependent PR, these changes will be merged into the original PR branch part-1-windows-fixes.

This PR will be automatically closed if the original PR is merged.

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📄 1,729% (17.29x) speedup for generate_candidates in codeflash/code_utils/coverage_utils.py

⏱️ Runtime : 247 milliseconds → 13.5 milliseconds (best of 165 runs)

📝 Explanation and details

Here’s a rewritten version of your program optimized for speed and minimal memory usage.

• Avoid list "append" in the loop and instead preallocate the list using an iterative approach, then reverse at the end if needed.
• Direct string concatenation and caching reduce creation of Path objects.
• Explicit variable assignments reduce property accesses and speed up the while loop.

Optimized code.

What changed:

• Avoided repeated property accesses by caching parent.
• Used string formatting (which benchmarks very well in 3.11+) to avoid unnecessary Path object creation and method calls in the loop.
• Otherwise, maintained the exact function signature and return values.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 40 Passed
🌀 Generated Regression Tests	✅ 1044 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	✅ 1 Passed
📊 Tests Coverage	100.0%

⚙️ Existing Unit Tests and Runtime

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
codeflash_concolic__c_sfar6/tmpr6mg7xpe/test_concolic_coverage.py::test_generate_candidates	5.62μs	5.51μs	✅2.00%
test_code_utils.py::test_generate_candidates	71.7μs	17.7μs	✅305%

🌀 Generated Regression Tests and Runtime

from __future__ import annotations

from pathlib import Path

# imports
import pytest  # used for our unit tests
from codeflash.code_utils.coverage_utils import generate_candidates

# --------------------------
# UNIT TESTS FOR generate_candidates
# --------------------------

# Basic Test Cases

def test_single_file_in_root():
    # File directly in root (e.g., /foo.py)
    path = Path("/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 5.32μs -> 5.03μs (5.77% faster)

def test_file_in_one_subdir():
    # File in one subdirectory (e.g., /bar/foo.py)
    path = Path("/bar/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 16.7μs -> 6.92μs (141% faster)

def test_file_in_two_subdirs():
    # File in two subdirectories (e.g., /baz/bar/foo.py)
    path = Path("/baz/bar/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.6μs -> 8.36μs (195% faster)

def test_file_with_multiple_extensions():
    # File with multiple dots (e.g., /baz/bar/foo.test.py)
    path = Path("/baz/bar/foo.test.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.7μs -> 8.32μs (196% faster)

def test_file_with_spaces_and_unicode():
    # File with spaces and unicode (e.g., /bär/ba z/foo ü.py)
    path = Path("/bär/ba z/foo ü.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 25.0μs -> 8.47μs (195% faster)

# Edge Test Cases

def test_file_at_relative_path():
    # Relative path (e.g., foo.py)
    path = Path("foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 5.94μs -> 5.73μs (3.66% faster)

def test_file_in_relative_subdir():
    # Relative path in subdir (e.g., bar/foo.py)
    path = Path("bar/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 16.5μs -> 7.69μs (114% faster)

def test_file_in_deep_relative_path():
    # Deep relative path (e.g., a/b/c/d/e.py)
    path = Path("a/b/c/d/e.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 38.9μs -> 12.3μs (216% faster)

def test_file_in_dot_slash_path():
    # Path with ./ (e.g., ./foo.py)
    path = Path("./foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 5.85μs -> 5.60μs (4.46% faster)

def test_file_in_dot_dot_path():
    # Path with ../bar/foo.py
    path = Path("../bar/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.9μs -> 9.27μs (169% faster)

def test_file_with_empty_string():
    # Empty string as path
    path = Path("")
    codeflash_output = generate_candidates(path); result = codeflash_output # 5.61μs -> 5.29μs (6.05% faster)
    
def test_file_with_hidden_dirs_and_files():
    # Hidden directories and files (e.g., /.hidden/.bar/.foo.py)
    path = Path("/.hidden/.bar/.foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.3μs -> 8.41μs (189% faster)

def test_file_with_trailing_slash():
    # Path ending with a slash (should be treated as a directory, not a file)
    path = Path("/bar/foo.py/")
    # Pathlib will treat this as a directory, so name will be "foo.py"
    # But if it's a directory, it's not a file, so let's see behavior
    codeflash_output = generate_candidates(path); result = codeflash_output # 15.8μs -> 6.55μs (142% faster)

def test_file_with_dot_as_filename():
    # File named '.' (rare, but possible)
    path = Path("/bar/.")
    codeflash_output = generate_candidates(path); result = codeflash_output # 4.84μs -> 4.64μs (4.31% faster)
    
def test_file_with_parent_as_root():
    # File at / (root), parent is itself
    path = Path("/foo.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 4.94μs -> 4.72μs (4.66% faster)

def test_file_with_drive_letter_windows_style():
    # Windows style path with drive letter
    path = Path("C:/foo/bar/baz.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 32.9μs -> 10.6μs (212% faster)

# Large Scale Test Cases

def test_deeply_nested_path():
    # Deeply nested path, e.g., 50 directories deep
    dirs = [f"dir{i}" for i in range(50)]
    path = Path("/" + "/".join(dirs) + "/file.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 499μs -> 78.1μs (540% faster)
    # Should have 51 candidates: file.py, dir49/file.py, ..., dir0/dir1/.../dir49/file.py
    expected = ["file.py"]
    for i in range(49, -1, -1):
        expected.append("/".join(dirs[i:]) + "/file.py")

def test_large_number_of_candidates_performance():
    # Test with 999 directories (max allowed for the test)
    dirs = [f"d{i}" for i in range(999)]
    path = Path("/" + "/".join(dirs) + "/x.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 76.1ms -> 2.59ms (2834% faster)
    # Should have 1000 candidates
    expected = ["x.py"]
    for i in range(998, -1, -1):
        expected.append("/".join(dirs[i:]) + "/x.py")

def test_large_file_name():
    # Very long file name
    file_name = "a" * 200 + ".py"
    path = Path("/foo/bar/" + file_name)
    codeflash_output = generate_candidates(path); result = codeflash_output # 26.7μs -> 9.43μs (183% faster)

def test_large_unicode_path():
    # Large unicode path
    dirs = [f"ü{i}" for i in range(10)]
    file_name = "файл.py"
    path = Path("/" + "/".join(dirs) + "/" + file_name)
    codeflash_output = generate_candidates(path); result = codeflash_output # 86.8μs -> 20.3μs (327% faster)
    expected = [file_name]
    for i in range(9, -1, -1):
        expected.append("/".join(dirs[i:]) + "/" + file_name)

# Regression/Mutation Tests

def test_mutation_wrong_order():
    # If the function returns candidates in reverse order, it should fail
    path = Path("/a/b/c.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 25.5μs -> 8.87μs (188% faster)

def test_mutation_wrong_separator():
    # If the function uses backslash instead of forward slash, it should fail
    path = Path("/a/b/c.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.0μs -> 8.42μs (186% faster)
    for candidate in result:
        pass

def test_mutation_missing_candidates():
    # If the function omits any candidate, it should fail
    path = Path("/foo/bar/baz.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 24.8μs -> 8.32μs (197% faster)

def test_mutation_extra_candidates():
    # If the function adds extra candidates, it should fail
    path = Path("/foo/bar/baz.py")
    codeflash_output = generate_candidates(path); result = codeflash_output # 23.6μs -> 8.29μs (185% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

from __future__ import annotations

from pathlib import Path

# imports
import pytest  # used for our unit tests
from codeflash.code_utils.coverage_utils import generate_candidates

# unit tests

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

def test_single_file_in_root():
    # Basic: File at root directory
    path = Path("foo.py")
    expected = ["foo.py"]
    codeflash_output = generate_candidates(path) # 6.17μs -> 5.83μs (5.85% faster)

def test_file_in_one_subdirectory():
    # Basic: File in one subdirectory
    path = Path("bar/foo.py")
    expected = ["foo.py", "bar/foo.py"]
    codeflash_output = generate_candidates(path) # 17.3μs -> 8.02μs (115% faster)

def test_file_in_two_subdirectories():
    # Basic: File in two nested subdirectories
    path = Path("baz/bar/foo.py")
    expected = ["foo.py", "bar/foo.py", "baz/bar/foo.py"]
    codeflash_output = generate_candidates(path) # 25.1μs -> 9.53μs (163% faster)

def test_file_with_extensionless_name():
    # Basic: File with no extension
    path = Path("src/main")
    expected = ["main", "src/main"]
    codeflash_output = generate_candidates(path) # 16.5μs -> 7.68μs (115% faster)

def test_file_with_dot_in_name():
    # Basic: File with dot in the name
    path = Path("src/my.module.py")
    expected = ["my.module.py", "src/my.module.py"]
    codeflash_output = generate_candidates(path) # 16.5μs -> 7.57μs (117% faster)

def test_file_with_multiple_dots_and_nested():
    # Basic: File with multiple dots in nested directory
    path = Path("a.b/c.d/e.f.py")
    expected = ["e.f.py", "c.d/e.f.py", "a.b/c.d/e.f.py"]
    codeflash_output = generate_candidates(path) # 25.0μs -> 9.13μs (174% faster)

# ----------- EDGE TEST CASES -----------

def test_file_in_deep_directory():
    # Edge: Deeply nested file
    path = Path("a/b/c/d/e/f/g/h/i/j/foo.py")
    expected = [
        "foo.py",
        "j/foo.py",
        "i/j/foo.py",
        "h/i/j/foo.py",
        "g/h/i/j/foo.py",
        "f/g/h/i/j/foo.py",
        "e/f/g/h/i/j/foo.py",
        "d/e/f/g/h/i/j/foo.py",
        "c/d/e/f/g/h/i/j/foo.py",
        "b/c/d/e/f/g/h/i/j/foo.py",
        "a/b/c/d/e/f/g/h/i/j/foo.py",
    ]
    codeflash_output = generate_candidates(path) # 83.4μs -> 20.8μs (302% faster)

def test_file_with_empty_path():
    # Edge: Empty path string
    path = Path("")
    expected = [""]  # Path("").name == ""
    codeflash_output = generate_candidates(path) # 5.47μs -> 5.46μs (0.183% faster)

def test_file_with_trailing_slash():
    # Edge: Path with trailing slash (should treat as directory, not file)
    path = Path("src/bar/")
    # Path("src/bar/").name == "bar"
    expected = ["bar", "src/bar"]
    codeflash_output = generate_candidates(path) # 16.3μs -> 7.74μs (111% faster)

def test_file_with_leading_slash():
    # Edge: Absolute path (Unix style)
    path = Path("/usr/local/bin/foo.py")
    expected = [
        "foo.py",
        "bin/foo.py",
        "local/bin/foo.py",
        "usr/local/bin/foo.py",
    ]
    codeflash_output = generate_candidates(path) # 32.0μs -> 9.88μs (224% faster)

def test_file_with_windows_drive_letter():
    # Edge: Windows drive letter
    path = Path("C:/Users/John/Documents/foo.py")
    expected = [
        "foo.py",
        "Documents/foo.py",
        "John/Documents/foo.py",
        "Users/John/Documents/foo.py",
        "C:/Users/John/Documents/foo.py",
    ]
    codeflash_output = generate_candidates(path) # 39.8μs -> 12.2μs (228% faster)

def test_file_with_dot_and_dotdot():
    # Edge: Path with "." and ".." components
    path = Path("src/./lib/../foo.py")
    # Path resolves to src/foo.py
    normalized = path.resolve().relative_to(Path.cwd())
    codeflash_output = generate_candidates(normalized); expected = codeflash_output # 15.7μs -> 7.31μs (114% faster)
    codeflash_output = generate_candidates(path); actual = codeflash_output # 26.6μs -> 7.57μs (251% faster)

def test_file_with_unicode_characters():
    # Edge: Unicode characters in file and directory names
    path = Path("dír/子目录/файл.py")
    expected = ["файл.py", "子目录/файл.py", "dír/子目录/файл.py"]
    codeflash_output = generate_candidates(path) # 26.1μs -> 9.43μs (177% faster)

def test_file_is_directory():
    # Edge: Path points to a directory, not a file
    path = Path("src")
    expected = ["src"]
    codeflash_output = generate_candidates(path) # 5.75μs -> 5.70μs (0.877% faster)

def test_file_with_only_name():
    # Edge: Path is just a filename, no directory
    path = Path("foo")
    expected = ["foo"]
    codeflash_output = generate_candidates(path) # 5.81μs -> 5.53μs (5.08% faster)

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

def test_deeply_nested_large_path():
    # Large: Path with 1000 nested directories
    dirs = [f"dir{i}" for i in range(1, 1001)]
    path = Path("/".join(dirs + ["file.py"]))
    # Build expected result
    expected = ["file.py"]
    for i in range(1, 1001):
        candidate = "/".join(dirs[-i:] + ["file.py"])
        expected.append(candidate)
    codeflash_output = generate_candidates(path)

def test_many_sibling_files():
    # Large: Generate candidates for many sibling files (ensures function is not affected by siblings)
    base = Path("dir/subdir")
    files = [base / f"file_{i}.py" for i in range(1000)]
    for i, path in enumerate(files):
        expected = [
            f"file_{i}.py",
            f"subdir/file_{i}.py",
            f"dir/subdir/file_{i}.py"
        ]
        codeflash_output = generate_candidates(path)

def test_long_file_name():
    # Large: File with a very long name
    long_name = "a" * 255 + ".py"
    path = Path(f"src/{long_name}")
    expected = [long_name, f"src/{long_name}"]
    codeflash_output = generate_candidates(path) # 18.4μs -> 8.79μs (110% faster)

def test_large_number_of_nested_dirs_and_long_file():
    # Large: Deep path and long file name
    dirs = [f"d{i}" for i in range(50)]
    long_name = "b" * 200 + ".py"
    path = Path("/".join(dirs + [long_name]))
    expected = [long_name]
    for i in range(1, 51):
        candidate = "/".join(dirs[-i:] + [long_name])
        expected.append(candidate)
    codeflash_output = generate_candidates(path)

def test_performance_on_large_path(monkeypatch):
    # Large: Performance test with 999 directories (should not hang or be too slow)
    dirs = [f"x{i}" for i in range(999)]
    path = Path("/".join(dirs + ["foo.py"]))
    codeflash_output = generate_candidates(path); result = codeflash_output # 77.4ms -> 2.61ms (2861% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

from codeflash.code_utils.coverage_utils import generate_candidates
from pathlib import Path

def test_generate_candidates():
    generate_candidates(Path())

To edit these changes git checkout codeflash/optimize-pr363-2025-06-22T22.47.46 and push.

[KRRT7]

local assigment might sometimes be faster but I think it mostly ends with with less readable code.