⚡️ Speed up function `format_runtime_comment` by 10% in PR #1624 (`codeflash/optimize-pr1199-2026-02-20T21.40.16`) by codeflash-ai[bot] · Pull Request #1625 · codeflash-ai/codeflash

codeflash-ai · 2026-02-20T21:47:47Z

⚡️ This pull request contains optimizations for PR #1624

If you approve this dependent PR, these changes will be merged into the original PR branch codeflash/optimize-pr1199-2026-02-20T21.40.16.

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

📄 10% (0.10x) speedup for `format_runtime_comment` in `codeflash/code_utils/time_utils.py`

⏱️ Runtime : 1.93 milliseconds → 1.75 milliseconds (best of 250 runs)

📝 Explanation and details

The optimized code achieves a 10% reduction in runtime (from 1.93ms to 1.75ms) by restructuring the format_time function to minimize floating-point operations and improve branch prediction.

Key optimizations:

Direct threshold comparisons: Instead of computing intermediate float values (value = nanoseconds / 1_000) and then checking thresholds on that value, the optimized version checks raw nanosecond thresholds directly (e.g., nanoseconds < 10_000 instead of value < 10). This avoids unnecessary division operations when they won't be used in the final format string.
Integer division for whole numbers: When formatting doesn't require decimal places (e.g., "123μs" vs "1.23μs"), the optimized version uses integer division (//) instead of float division (/), which is faster and avoids float-to-int conversion overhead.
Eliminated conditional expressions: The original code used nested ternary operators (f"{value:.2f}μs" if value < 10 else ...), which require evaluating the condition twice (once for the threshold, once for the format string). The optimized version uses explicit if-statements with direct return paths, improving branch prediction and reducing repeated comparisons.

Performance impact by test case:

The largest gains appear in the test_large_scale_many_calls_return_valid_strings test (12.1% faster), which makes 1000 format calls with varying magnitudes. This demonstrates the cumulative benefit when format_time is called repeatedly.
Most individual test cases show 2-8% improvements, confirming consistent gains across different input ranges (nanoseconds, microseconds, milliseconds, seconds).
The optimization is particularly effective for values in the microsecond range (most common in the test data), where the original code performed the most redundant float divisions.

Why this matters:
Line profiler data shows that the original code spent 31.8% of format_time execution time on the microsecond formatting line alone (the ternary expression). The optimized version distributes this work across more efficient branches, reducing per-hit time from 505.4ns to individual branch costs of 124-306ns. The function is likely called in performance-sensitive contexts (formatting profiling results, logging), so even a 10% improvement compounds when called thousands of times during analysis workflows.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 1208 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Click to see Generated Regression Tests

import re

import pytest  # used for our unit tests
from codeflash.code_utils.time_utils import format_runtime_comment

def test_basic_ns_level_faster():
    # 500ns original -> 250ns optimized; optimized is faster.
    # performance_gain = (500-250)/250 = 1 -> 100%
    # format_time produces "500ns" and "250ns" for these integers.
    codeflash_output = format_runtime_comment(500, 250); result = codeflash_output # 3.90μs -> 3.95μs (1.29% slower)

def test_basic_ms_level_faster_and_formatting():
    # 1_500_000ns (1.50ms) original -> 500_000ns (0.50ms) optimized
    # performance_gain = (1_500_000 - 500_000)/500_000 = 2 -> 200%
    codeflash_output = format_runtime_comment(1_500_000, 500_000); result = codeflash_output # 4.90μs -> 4.59μs (6.76% faster)

def test_custom_prefix_and_slower_status_seconds():
    # original 1s -> optimized 2s (slower)
    # performance_gain = (1e9 - 2e9) / 2e9 = -0.5 -> displayed as 50.0% (abs + one decimal)
    codeflash_output = format_runtime_comment(1_000_000_000, 2_000_000_000, comment_prefix="//"); result = codeflash_output # 5.16μs -> 5.10μs (1.16% faster)

def test_optimized_zero_avoids_division_and_formats_zero_ns():
    # When optimized_time_ns == 0, performance_gain returns 0.0 by design.
    # original 1000ns -> 1.00μs ; optimized 0ns -> "0ns"
    codeflash_output = format_runtime_comment(1000, 0); result = codeflash_output # 4.41μs -> 4.36μs (1.17% faster)

def test_negative_input_raises_value_error():
    # Negative nanoseconds are invalid for format_time and should raise ValueError.
    with pytest.raises(ValueError):
        format_runtime_comment(-1, 100) # 5.16μs -> 5.09μs (1.40% faster)

    with pytest.raises(ValueError):
        format_runtime_comment(100, -50) # 3.21μs -> 3.23μs (0.620% slower)

def test_non_int_input_raises_type_error():
    # Non-integer inputs should raise TypeError from format_time when called.
    with pytest.raises(TypeError):
        format_runtime_comment(100.0, 50) # 4.91μs -> 4.77μs (2.94% faster)

    with pytest.raises(TypeError):
        format_runtime_comment(100, "50") # 2.48μs -> 2.44μs (1.64% faster)

def test_microsecond_formatting_thresholds():
    # Test the μs rounding / branch thresholds:
    # 10_000 ns -> 10.0μs (uses one decimal because value == 10)
    # 9_000 ns -> 9.00μs (uses two decimals because value < 10)
    codeflash_output = format_runtime_comment(10_000, 9_000); result = codeflash_output # 4.96μs -> 4.83μs (2.69% faster)

def test_millisecond_to_integer_ms_boundary():
    # 100_000_000 ns => 100ms (integer formatting for >=100)
    # 50_000_000 ns => 50.0ms (one decimal for <100 and >=10)
    codeflash_output = format_runtime_comment(100_000_000, 50_000_000); result = codeflash_output # 4.51μs -> 4.29μs (5.13% faster)

def test_large_scale_many_calls_return_valid_strings():
    # Make 1000 deterministic calls and validate that each result is syntactically correct.
    # We avoid randomness to keep the test deterministic.
    regex = re.compile(r"^[#@]\s.+ -> .+ \(\-?\d+(?:\.\d+)?% (?:faster|slower)\)$")
    # We will alternate prefixes to ensure prefix handling doesn't break at scale.
    prefixes = ["#", "@"]  # limited two prefixes used repeatedly
    results = []
    for i in range(1, 1001):  # 1000 iterations
        # Construct deterministic original and optimized times:
        # - Vary magnitude up to millions of ns to exercise μs/ms/s formatting branches.
        original = i * 1_000  # grows linearly (>=1000 -> μs+)
        # Make optimized slightly smaller or larger depending on parity to flip faster/slower
        optimized = original - (i % 5)  # ensure some differences and occasionally zero-ish values
        if optimized < 0:
            optimized = 0
        prefix = prefixes[i % len(prefixes)]
        codeflash_output = format_runtime_comment(original, optimized, comment_prefix=prefix); s = codeflash_output # 1.47ms -> 1.31ms (12.1% faster)
        results.append(s)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

import pytest
from codeflash.code_utils.time_utils import (format_perf,
                                             format_runtime_comment,
                                             format_time)

def test_basic_improvement_faster():
    """Test basic case where optimized code is faster."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=500_000); result = codeflash_output # 5.53μs -> 5.29μs (4.54% faster)

def test_basic_degradation_slower():
    """Test basic case where optimized code is slower."""
    codeflash_output = format_runtime_comment(original_time_ns=500_000, optimized_time_ns=1_000_000); result = codeflash_output # 5.27μs -> 4.97μs (6.04% faster)

def test_custom_comment_prefix():
    """Test that custom comment prefix is used."""
    codeflash_output = format_runtime_comment(
        original_time_ns=1_000_000,
        optimized_time_ns=500_000,
        comment_prefix="//"
    ); result = codeflash_output # 5.09μs -> 4.84μs (5.19% faster)

def test_default_comment_prefix():
    """Test that default comment prefix '#' is used."""
    codeflash_output = format_runtime_comment(
        original_time_ns=1_000_000,
        optimized_time_ns=500_000
    ); result = codeflash_output # 4.99μs -> 4.49μs (11.2% faster)

def test_format_includes_arrow():
    """Test that format includes arrow separator between times."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=500_000); result = codeflash_output # 4.80μs -> 4.51μs (6.43% faster)

def test_format_includes_percentage():
    """Test that format includes percentage in parentheses."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=500_000); result = codeflash_output # 4.67μs -> 4.53μs (3.09% faster)

def test_equal_times():
    """Test when original and optimized times are equal."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=1_000_000); result = codeflash_output # 4.49μs -> 4.45μs (0.922% faster)

def test_very_small_nanoseconds():
    """Test with very small nanosecond values (< 1000)."""
    codeflash_output = format_runtime_comment(original_time_ns=500, optimized_time_ns=100); result = codeflash_output # 3.85μs -> 3.77μs (2.15% faster)

def test_microseconds_range():
    """Test with values in microsecond range (1000 to 1_000_000)."""
    codeflash_output = format_runtime_comment(original_time_ns=10_000, optimized_time_ns=5_000); result = codeflash_output # 4.85μs -> 4.72μs (2.75% faster)

def test_milliseconds_range():
    """Test with values in millisecond range (1_000_000 to 1_000_000_000)."""
    codeflash_output = format_runtime_comment(original_time_ns=10_000_000, optimized_time_ns=5_000_000); result = codeflash_output # 4.36μs -> 4.43μs (1.60% slower)

def test_seconds_range():
    """Test with values in second range (>= 1_000_000_000)."""
    codeflash_output = format_runtime_comment(original_time_ns=2_000_000_000, optimized_time_ns=1_000_000_000); result = codeflash_output # 4.68μs -> 4.75μs (1.47% slower)

def test_huge_time_difference():
    """Test with very large difference in times."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000_000, optimized_time_ns=1_000); result = codeflash_output # 4.93μs -> 4.95μs (0.404% slower)

def test_small_improvement():
    """Test with very small performance improvement."""
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=999_000); result = codeflash_output # 5.11μs -> 4.88μs (4.71% faster)

def test_small_degradation():
    """Test with very small performance degradation."""
    codeflash_output = format_runtime_comment(original_time_ns=999_000, optimized_time_ns=1_000_000); result = codeflash_output # 5.03μs -> 4.78μs (5.23% faster)

def test_zero_optimized_time():
    """Test when optimized time is zero (should not crash)."""
    # This is an edge case - optimized_time_ns of 0
    # The performance_gain function returns 0.0 when optimized_runtime_ns is 0
    codeflash_output = format_runtime_comment(original_time_ns=1_000_000, optimized_time_ns=0); result = codeflash_output # 4.15μs -> 4.25μs (2.33% slower)

def test_zero_original_time():
    """Test when original time is zero."""
    codeflash_output = format_runtime_comment(original_time_ns=0, optimized_time_ns=1_000_000); result = codeflash_output # 4.30μs -> 4.26μs (0.939% faster)

def test_both_times_zero():
    """Test when both times are zero."""
    codeflash_output = format_runtime_comment(original_time_ns=0, optimized_time_ns=0); result = codeflash_output # 3.47μs -> 3.44μs (0.844% faster)

def test_empty_string_prefix():
    """Test with empty string as comment prefix."""
    codeflash_output = format_runtime_comment(
        original_time_ns=1_000_000,
        optimized_time_ns=500_000,
        comment_prefix=""
    ); result = codeflash_output # 5.14μs -> 4.96μs (3.63% faster)

def test_multichar_prefix():
    """Test with multi-character prefix."""
    codeflash_output = format_runtime_comment(
        original_time_ns=1_000_000,
        optimized_time_ns=500_000,
        comment_prefix="### NOTE:"
    ); result = codeflash_output # 4.85μs -> 4.49μs (8.04% faster)

def test_special_char_prefix():
    """Test with special character prefix."""
    codeflash_output = format_runtime_comment(
        original_time_ns=1_000_000,
        optimized_time_ns=500_000,
        comment_prefix="!!"
    ); result = codeflash_output # 4.69μs -> 4.57μs (2.65% faster)

def test_large_original_time():
    """Test with extremely large original time."""
    codeflash_output = format_runtime_comment(
        original_time_ns=999_999_999_999,
        optimized_time_ns=500_000_000_000
    ); result = codeflash_output # 5.14μs -> 5.03μs (2.19% faster)

def test_large_optimized_time():
    """Test with extremely large optimized time."""
    codeflash_output = format_runtime_comment(
        original_time_ns=500_000_000_000,
        optimized_time_ns=999_999_999_999
    ); result = codeflash_output # 4.69μs -> 4.82μs (2.70% slower)

def test_many_format_calls():
    """Test performance with many sequential calls."""
    # Create 100 pairs of times and format them all
    for i in range(100):
        original = 1_000_000 * (i + 1)
        optimized = 500_000 * (i + 1)
        codeflash_output = format_runtime_comment(original_time_ns=original, optimized_time_ns=optimized); result = codeflash_output # 164μs -> 156μs (5.45% faster)

def test_varying_time_scales():
    """Test with varied time scales across multiple calls."""
    # Test across all time unit scales
    time_pairs = [
        (100, 50),           # nanoseconds
        (10_000, 5_000),     # microseconds
        (10_000_000, 5_000_000),  # milliseconds
        (10_000_000_000, 5_000_000_000),  # seconds
    ]
    for original, optimized in time_pairs:
        codeflash_output = format_runtime_comment(original_time_ns=original, optimized_time_ns=optimized); result = codeflash_output # 11.3μs -> 11.0μs (2.65% faster)

def test_consistent_format_structure():
    """Test that format is consistent across many calls."""
    # All results should follow the same structure pattern
    for i in range(50):
        codeflash_output = format_runtime_comment(
            original_time_ns=1_000_000 + i * 100_000,
            optimized_time_ns=500_000 + i * 50_000
        ); result = codeflash_output # 83.4μs -> 79.2μs (5.35% faster)

def test_boundary_time_values():
    """Test with time values at unit boundaries."""
    # Test at exact boundary values between units
    boundaries = [
        (999, 500),                    # just under 1μs
        (1_000, 500),                  # exactly 1μs
        (1_001, 500),                  # just over 1μs
        (999_999, 500_000),            # just under 1ms
        (1_000_000, 500_000),          # exactly 1ms
        (1_000_001, 500_000),          # just over 1ms
        (999_999_999, 500_000_000),    # just under 1s
        (1_000_000_000, 500_000_000),  # exactly 1s
        (1_000_000_001, 500_000_000),  # just over 1s
    ]
    for original, optimized in boundaries:
        codeflash_output = format_runtime_comment(original_time_ns=original, optimized_time_ns=optimized); result = codeflash_output # 19.5μs -> 18.2μs (7.22% faster)

def test_various_prefixes_scalability():
    """Test with various prefix styles across multiple calls."""
    prefixes = ["#", "//", "/*", "<!---", ";;", "```", "", ">>>"]
    for prefix in prefixes:
        codeflash_output = format_runtime_comment(
            original_time_ns=1_000_000,
            optimized_time_ns=500_000,
            comment_prefix=prefix
        ); result = codeflash_output # 17.1μs -> 15.7μs (8.73% faster)

def test_ratio_preservation_multiple_calls():
    """Test that percentage gain is correctly calculated across varying ratios."""
    # Test different improvement ratios
    ratios = [
        (1_000_000, 500_000),    # 100% improvement
        (1_000_000, 750_000),    # 33.33% improvement
        (1_000_000, 900_000),    # 11.11% improvement
        (1_000_000, 999_000),    # 0.1% improvement
        (500_000, 1_000_000),    # -50% (degradation)
    ]
    for original, optimized in ratios:
        codeflash_output = format_runtime_comment(original_time_ns=original, optimized_time_ns=optimized); result = codeflash_output # 12.9μs -> 12.1μs (6.79% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-pr1624-2026-02-20T21.47.41 and push.

The optimized code achieves a **10% reduction in runtime** (from 1.93ms to 1.75ms) by restructuring the `format_time` function to minimize floating-point operations and improve branch prediction. **Key optimizations:** 1. **Direct threshold comparisons**: Instead of computing intermediate float values (`value = nanoseconds / 1_000`) and then checking thresholds on that value, the optimized version checks raw nanosecond thresholds directly (e.g., `nanoseconds < 10_000` instead of `value < 10`). This avoids unnecessary division operations when they won't be used in the final format string. 2. **Integer division for whole numbers**: When formatting doesn't require decimal places (e.g., "123μs" vs "1.23μs"), the optimized version uses integer division (`//`) instead of float division (`/`), which is faster and avoids float-to-int conversion overhead. 3. **Eliminated conditional expressions**: The original code used nested ternary operators (`f"{value:.2f}μs" if value < 10 else ...`), which require evaluating the condition twice (once for the threshold, once for the format string). The optimized version uses explicit if-statements with direct return paths, improving branch prediction and reducing repeated comparisons. **Performance impact by test case:** - The largest gains appear in the `test_large_scale_many_calls_return_valid_strings` test (12.1% faster), which makes 1000 format calls with varying magnitudes. This demonstrates the cumulative benefit when `format_time` is called repeatedly. - Most individual test cases show 2-8% improvements, confirming consistent gains across different input ranges (nanoseconds, microseconds, milliseconds, seconds). - The optimization is particularly effective for values in the microsecond range (most common in the test data), where the original code performed the most redundant float divisions. **Why this matters:** Line profiler data shows that the original code spent 31.8% of `format_time` execution time on the microsecond formatting line alone (the ternary expression). The optimized version distributes this work across more efficient branches, reducing per-hit time from 505.4ns to individual branch costs of 124-306ns. The function is likely called in performance-sensitive contexts (formatting profiling results, logging), so even a 10% improvement compounds when called thousands of times during analysis workflows.

claude · 2026-02-20T22:00:07Z

PR Review Summary

Prek Checks

✅ All prek checks passed (ruff check and ruff format) — no issues found.

Mypy

⚠️ 411 mypy errors across all changed files in this PR (most from the large Java support addition in the base branch). The single file changed in this PR's commit (codeflash/code_utils/time_utils.py) has no new mypy errors introduced.

Code Review

✅ No critical issues found.

The optimization restructures format_time() from nested ternaries to explicit if-chains with direct nanosecond threshold comparisons:

Logic equivalence: value < 10 → nanoseconds < 10_000 (equivalent), same pattern for all thresholds
Integer division: int(value) replaced with nanoseconds // 1_000 — equivalent for positive integers
Seconds range: Added explicit branches for >=10s and >=100s (previously the fallthrough only handled <10s, <100s, and >=100s in one ternary)

No bugs, security issues, or breaking changes.

Test Coverage

File	Stmts	Miss	Coverage	Notes
`codeflash/code_utils/time_utils.py`	85	4	95%	Changed lines (77-92) fully covered ✅

Missing lines: 52 (in humanize_runtime, pre-existing) and 109-113 (format_runtime_comment function, pre-existing — not changed in this PR's diff)
Changed lines coverage: All restructured format_time branches (lines 77-92) are exercised by existing tests
No coverage regression from this optimization

Last updated: 2026-02-20

codeflash-ai bot added ⚡️ codeflash Optimization PR opened by Codeflash AI 🎯 Quality: High Optimization Quality according to Codeflash labels Feb 20, 2026

codeflash-ai bot mentioned this pull request Feb 20, 2026

⚡️ Speed up method PrComment.to_json by 28% in PR #1199 (omni-java) #1624

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⚡️ Speed up function `format_runtime_comment` by 10% in PR #1624 (`codeflash/optimize-pr1199-2026-02-20T21.40.16`)#1625

⚡️ Speed up function `format_runtime_comment` by 10% in PR #1624 (`codeflash/optimize-pr1199-2026-02-20T21.40.16`)#1625
codeflash-ai[bot] wants to merge 1 commit intocodeflash/optimize-pr1199-2026-02-20T21.40.16from
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codeflash-ai bot commented Feb 20, 2026

⚡️ This pull request contains optimizations for PR #1624

📄 10% (0.10x) speedup for format_runtime_comment in codeflash/code_utils/time_utils.py

📝 Explanation and details

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claude bot commented Feb 20, 2026

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📄 10% (0.10x) speedup for `format_runtime_comment` in `codeflash/code_utils/time_utils.py`