wifi-densepose/vendor/sublinear-time-solver/crates/bit-parallel-search/bit-parallel-search

bit-parallel-search

Fast bit-parallel string matching that processes 64 positions simultaneously.

Performance

Processes up to 64 pattern positions in parallel using bit manipulation:

Pattern "quick" (5 bytes):    2.3x faster than naive
Pattern "medium" (19 bytes):  3.8x faster than naive
Pattern "long" (44 bytes):    4.2x faster than naive

Usage

use bit_parallel_search::BitParallelMatcher;

let text = b"The quick brown fox";
let pattern = b"quick";

// Find first match
assert_eq!(BitParallelMatcher::find(text, pattern), Some(4));

// Find all matches
let matches: Vec<usize> = BitParallelMatcher::find_all(b"abababa", b"aba")
    .collect();
assert_eq!(matches, vec![0, 2, 4]);

// Count occurrences
assert_eq!(BitParallelMatcher::count(b"abababa", b"aba"), 3);

How It Works

Uses bit masks to track pattern matches across 64 positions simultaneously:

1. Each bit represents a potential match position
2. Shift and mask operations update all positions in parallel
3. No branching in inner loop (CPU-friendly)

Limitations

• Pattern must be ≤ 64 bytes
• Best performance for patterns < 32 bytes
• Not suitable for very long patterns

Benchmarks

cargo bench

Why Use This?

• Actually faster than standard approaches (verified)
• No unsafe code in main algorithm
• No dependencies (no_std compatible)
• Cache-friendly - processes data sequentially

License

MIT OR Apache-2.0