KHR_parallel_shader_compile extension

The KHR_parallel_shader_compile extension is part of the WebGL API and enables a non-blocking poll operation, so that compile/link status availability (COMPLETION_STATUS_KHR) can be queried without potentially incurring stalls. In other words you can check the status of your shaders compiling without blocking the runtime.

WebGL extensions are available using the WebGLRenderingContext.getExtension() method. For more information, see also Using Extensions in the WebGL tutorial.

Constants

ext.COMPLETION_STATUS_KHR

A GLenum.

Examples

Enable the extension:

js
const ext = gl.getExtension("KHR_parallel_shader_compile");

In general, best practice with or without the extension is:

js
// Assuming lists of `shaders` and `programs`:
for (const x of shaders) gl.compileShader(x); // Never check compile status unless subsequent linking fails.
for (const x of programs) gl.linkProgram(x);

With the extension, apps would be able to poll whether programs have linked without janking, but these are likely to take the same total wall time to link:

js
// Generator yielding a progress ratio [0.0, 1.0].
// Without the extension, this will jank and only check one program per generation.
function* linkingProgress(programs) {
  const ext = gl.getExtension("KHR_parallel_shader_compile");
  let todo = programs.slice();
  while (todo.length) {
    if (ext) {
      todo = todo.filter(
        (x) => !gl.getProgramParameter(x, ext.COMPLETION_STATUS_KHR),
      );
    } else {
      const x = todo.pop();
      gl.getProgramParameter(x, gl.LINK_STATUS);
    }
    if (!todo.length) return;
    yield 1.0 - todo.length / programs.length;
  }
}

Specifications

Specification
WebGL KHR_parallel_shader_compile Extension Specification

Browser compatibility

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See also