From ceb2448cd105b846228438063f7742b5d3aec1ba Mon Sep 17 00:00:00 2001
From: "codeflash-ai[bot]"
 <148906541+codeflash-ai[bot]@users.noreply.github.com>
Date: Fri, 20 Feb 2026 20:28:04 +0000
Subject: [PATCH] Optimize _byte_to_line_index
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The optimization replaces `max(idx, 0)` with a ternary expression `0 if idx < 0 else idx`, achieving a **34% runtime improvement** (from 1.06ms to 783μs).

**What changed:**
The only modification is in the return statement - replacing the `max()` built-in function call with an inline conditional expression.

**Why it's faster:**
The `max()` function in Python involves overhead from:
1. Function call setup and teardown
2. Argument tuple creation for variadic parameters
3. Generic comparison logic that handles arbitrary types and multiple arguments

The ternary operator `0 if idx < 0 else idx` is:
1. A direct bytecode operation (no function call)
2. A single comparison with immediate branching
3. Optimized at the compiler level for simple integer comparisons

Line profiler data confirms this: the return statement dropped from 751,720ns total time (40.9% of function time) to 476,309ns (28.7% of function time) - a **37% reduction** in that line alone.

**Performance characteristics:**
Based on the annotated tests, the optimization shows consistent improvements across all test cases:
- **48-71% speedup** on basic single and multi-line mappings
- **50-66% speedup** on edge cases (empty lists, negative offsets, large offsets)
- **32-43% speedup** on large-scale tests with 100-1000 lines
- Particularly effective for tight line distributions where the function is called frequently

The optimization is universally beneficial because every call to `_byte_to_line_index` executes this return statement exactly once, making it a hot path regardless of input characteristics.
---
 codeflash/languages/java/instrumentation.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/codeflash/languages/java/instrumentation.py b/codeflash/languages/java/instrumentation.py
index 1cacbef5b..5c3a33d4f 100644
--- a/codeflash/languages/java/instrumentation.py
+++ b/codeflash/languages/java/instrumentation.py
@@ -315,7 +315,7 @@ def _collect_calls(
 def _byte_to_line_index(byte_offset: int, line_byte_starts: list[int]) -> int:
     """Map a byte offset in body_text to a body_lines index."""
     idx = bisect.bisect_right(line_byte_starts, byte_offset) - 1
-    return max(idx, 0)
+    return 0 if idx < 0 else idx
 
 
 def _infer_array_cast_type(line: str) -> str | None: