struct MatrixBatch {
  size: vec4<u32>,
  data: array<vec4<f32>>,
}

@group(0) @binding(0)
var<storage, read> m: MatrixBatch;
@group(0) @binding(1)
var<storage, read> dldm: MatrixBatch;
@group(0) @binding(2)
var<storage, read_write> grad: MatrixBatch;

@compute @workgroup_size(1)
fn main(@builtin(global_invocation_id) global_id: vec3<u32>) {
  grad.size = m.size;

  let vc = m.size.x / 4;
  let ro = (global_id.z * m.size.y + global_id.y) * vc;

  var s = 0f;
  for (var x = 0u; x < vc; x++) {
    s += dot(m.data[ro + x], dldm.data[ro + x]);
  }

  grad.data[ro + global_id.x] = m.data[ro + global_id.x] * (dldm.data[ro + global_id.x] - vec4(s));
}