Bound common-line pruning to the local window#47
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Fix should_prune_common_line() so the backward scan starts at pos.saturating_sub(WINDOW_SIZE) instead of the absolute WINDOW_SIZE index. The old bound made the scanned range grow with pos, which turned the preprocessing heuristic into an increasingly expensive rescan on highly repetitive inputs and caused the gix-merge clusterfuzz testcase to time out. Add a regression test that proves distant context outside the local window does not affect the pruning decision. Co-authored-by: GPT 5.4 <codex@openai.com>
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This is the v0.2 version of this v0.1 PR: #46. It's exactly the same.
Let's use one of these for communication.
Whlie I tested the performance of the v0.1 fix branch, I didn't do the same here.
Fix should_prune_common_line() so the backward scan starts at pos.saturating_sub(WINDOW_SIZE) instead of the absolute WINDOW_SIZE index.
The old bound made the scanned range grow with pos, which turned the preprocessing heuristic into an increasingly expensive rescan on highly repetitive inputs and caused the gix-merge clusterfuzz testcase to time out.
Add a regression test that proves distant context outside the local window does not affect the pruning decision.
#46