Rust for C-Programmers

22.8 SIMD (Single Instruction, Multiple Data)

SIMD operations let a single instruction process multiple data points at once. They’re useful for tasks like image processing or numeric loops.

22.8.1 Automatic vs. Manual SIMD

• Automatic: LLVM may auto-vectorize loops with high optimization settings (-C opt-level=3), depending on heuristics.
• Manual: You can use portable-simd of Rust’s standard library or other crates.

22.8.2 Example of Manual SIMD

Portable_simd requires still the nightly compiler.

#![feature(portable_simd)]
use std::simd::f32x4;
fn main() {
    let a = f32x4::splat(10.0);
    let b = f32x4::from_array([1.0, 2.0, 3.0, 4.0]);
    println!("{:?}", a + b);
}

Explanation: We construct our SIMD vectors with methods like splat or from_array. Next, we can use operators like + on them, and the appropriate SIMD instructions will be carried out.

For details see Portable-simd and the Guide.