Faster substring search with SIMD in Zig
13 days ago
- #Zig
- #Performance
- #SIMD
- The article explores implementing a faster substring search in Zig using SIMD (Single Instruction, Multiple Data) techniques.
- A baseline comparison is made with Zig's std.mem.indexOf function, which is the standard substring search method.
- The SIMD algorithm involves comparing the first and last characters of the needle (substring to find) with blocks of the haystack (text to search), reducing the number of checks needed.
- Implementation details include using AVX2 for 256-bit wide registers and Zig's @Vector and @splat functions for SIMD operations.
- Benchmarks show a 60% performance improvement with SIMD, especially noticeable in large texts like 'Moby Dick'.
- Optimizations include selecting rarer characters in the needle to reduce false positives and branch mispredictions, leading to further performance gains.
- The article discusses potential improvements with AVX-512 for even faster searches but notes limitations like platform dependency and the generic nature of std.mem.indexOf.
- Despite the performance benefits, the author concludes that SIMD substring search may not be worth integrating into Zig's standard library due to its niche use case and platform-specific requirements.