Performance & Benchmarks

symtrace is designed for ultra-low overhead execution, delivering instant semantic diffs on individual files while scaling sub-linearly on large multi-file changesets.

Empirical Benchmark Results (v0.3.0)

Tested on a production release build (LLVM -O3, LTO enabled) against the express repository (d:\rust_playground\express):

Scenario	Command	Files	AST Nodes	Parse Time	Diff Time	Total Time	Speedup Factor
Cold AST Parse	symtrace express HEAD~1 HEAD (Cold)	2	6,011	32.21 ms	0.94 ms	86.77 ms	Baseline
Warm Cache Hit	symtrace express HEAD~1 HEAD (Warm)	2	6,011	3.77 ms	1.24 ms	22.21 ms	3.91× faster
JSON Output	symtrace express HEAD~1 HEAD --json	2	6,011	3.66 ms	1.00 ms	18.38 ms	4.72× faster
Working Tree Diff	symtrace express HEAD (Single Commit)	0	0	0.01 ms	0.00 ms	142.88 ms	N/A
Full Test Suite	cargo test --all (166 tests)	N/A	~65,000	N/A	N/A	90.00 ms (0.09s)	166 tests / 90ms

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Architectural Performance Drivers

1. Parallel Execution (rayon) — Files and AST nodes are parsed, fingerprinted, and matched concurrently across all available CPU cores.
2. Two-Tier AST Caching — Recently parsed trees are cached in a 500-capacity in-memory LRU cache and persistent versioned disk cache (bincode serialized).
3. BLAKE3 SIMD Fingerprinting — Node hashes use SIMD-accelerated BLAKE3 hashing to process thousands of nodes per millisecond.
4. Arena Memory Allocation (bumpalo) — Zero-overhead tree construction avoids thousands of individual heap allocations.
5. Early Skipping — Identical file blobs across commits are bypassed prior to parsing.

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Performance Telemetry

Every run calculates precise timing stats visible in both terminal output and JSON telemetry:

Performance
  Files processed   : 2
  Nodes compared    : 6,011
  Parse time        : 3.77 ms
  Diff time         : 1.24 ms
  Total time        : 22.21 ms

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Resource Tuning Options

For large monorepos or untrusted codebases, resource limits prevent runaway memory or parsing hangs:

symtrace . HEAD~1 HEAD \
  --max-file-size 10485760 \
  --max-ast-nodes 500000 \
  --parse-timeout-ms 5000