Writing Kernels

A Kernel contains the WGSL code that runs on the GPU.

import { Kernel } from '@volten/core';

const scale = new Kernel(`
  fn main(gid: vec3u) {
    output[gid.x] = input[gid.x] * multiplier;
  }
`);

You write a main function. Volten adds the compute entry point, workgroup size, bindings, and safety guard around it.

Builtin Shorthands

Volten expands a few parameter names in main:

| Name | Type | Meaning | | --- | --- | --- | | gid | vec3u or vec3<u32> | Global invocation id | | lid | u32 | Local invocation index | | lid3 | vec3u or vec3<u32> | Local invocation id | | wid | vec3u or vec3<u32> | Workgroup id | | nwg | vec3u or vec3<u32> | Number of workgroups |

const kernel = new Kernel(`
  fn main(gid: vec3u, lid: u32) {
    data[gid.x] = f32(lid);
  }
`);

You can also write the full WGSL builtin syntax yourself.

fn main(@builtin(global_invocation_id) gid: vec3u) {
  data[gid.x] = data[gid.x] * 2.0;
}

Helper Functions

Only the function named main is treated as the kernel entry point. Other functions are left alone.

const kernel = new Kernel(`
  fn square(x: f32) -> f32 {
    return x * x;
  }

  fn main(gid: vec3u) {
    data[gid.x] = square(data[gid.x]);
  }
`);

Labels

Add a label when you want clearer debug output and browser GPU tooling names.

const kernel = new Kernel(`...`, {
    label: 'scale values'
});