Sep 0.10.0 was released April 22nd, 2025 with optimizations for AVX-512 capable CPUs like the AMD 9950X (Zen 5) and updated benchmarks including the 9950X. Sep now achieves a staggering 21 GB/s on the 9950X for the low-level CSV parsing. 🚀 Before 0.10.0, Sep achieved ~18 GB/s on 9950X.

In this blog post, I will dive into how .NET 9.0 machine code for AVX-512 is sub-optimal and what changes were made to speed up Sep for AVX-512 by circumventing this, showing interesting code and assembly along the way, so get ready for SIMD C# code, x64 SIMD assembly and tons of benchmark numbers.

Sep - GitHub

World’s Fastest .NET CSV Parser. Modern, minimal, fast, zero allocation, reading and writing of separated values (csv, tsv etc.). Cross-platform, trimmable and AOT/NativeAOT compatible.