perf: DFA FindAll early termination + prefilter skip#129
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…inputs findIndicesDFAAt used DFA.FindAt (longest-match O(n) scan) as prefilter, then PikeVM re-scanned for exact bounds. For FindAll on dense-match inputs (e.g., template patterns with 2000 matches over 50KB), total DFA work was ~50MB due to O(n^2) scanning. Fix: - Added DFA.IsMatchAt() with early termination — O(k) where k is distance to first match, vs O(n) for longest-match scan - Prefilter skip: when prefix prefilter available, jump PikeVM directly to candidate position instead of scanning from 'at' Template pattern FindAll improved ~37% (5.4ms -> 3.4ms). Remaining 2.8x gap vs stdlib is PikeVM per-byte cost (UTF-8 dot handling).
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Summary
findIndicesDFAAtas prefilter check, eliminating O(n²) total scanning in FindAll on dense-match inputs.{{), jump PikeVM directly to the candidate position instead of scanning fromat. Avoids PikeVM processing non-matching regions.\{\{(.*?)\}\}FindAll improved ~37% (5.4ms → 3.4ms on 50KB with 2000 matches)..handling) — separate optimization task.Follow-up to #128 (BoundedBacktracker span fix). Both reported by @kostya via #124.
Test plan
go test ./...— all 9 packages passgofmt -l .— no formatting issues