Mitchell Hashimoto: Every Developer Should Know SIMD
Original: Everyone should know SIMD
Why This Matters
Democratizing SIMD knowledge could meaningfully raise baseline software performance across the industry.
Mitchell Hashimoto argues in a July 2026 post that SIMD — a CPU technique for processing multiple values in parallel — is far simpler than its reputation suggests, and that all software engineers should learn its basic five-step pattern, not just high-performance specialists.
Mitchell Hashimoto, co-founder of HashiCorp and creator of Ghostty, published a detailed essay on July 22, 2026, asserting that SIMD (Single Instruction, Multiple Data) is broadly useful and accessible to everyday developers. SIMD allows a CPU to operate on multiple data values simultaneously — for example, comparing 8 bytes at once instead of one — yielding direct speedups of 4x, 8x, or more for loops over large arrays.
Hashimoto argues that most developers dismiss SIMD as niche or overly complex, but that the common use case follows a predictable five-step pattern: (1) broadcast constants and initialize accumulators, (2) loop over input one vector-width chunk at a time, (3) perform parallel operations across all lanes, (4) reduce or store the vector result, and (5) handle remaining elements with a normal scalar tail loop. He illustrates this pattern with a real example from Ghostty, processing decoded codepoints to find runs of printable characters.
The post uses Zig for code examples but notes the concepts apply across languages. Hashimoto also addresses why compilers cannot reliably auto-vectorize, making manual SIMD knowledge valuable. He cites projects like simdutf and simdjson as advanced examples, but emphasizes that everyday SIMD usage is far simpler. The post was written entirely without AI assistance.