I'm trying to use an uniform array of matrices in my compute shader. However, it's really slow. I've narrowed it down to this lines of code:
uniform mat4 someMatrixArray[64];
...
vec4 result = vec4(0);
for (int i = 0; i < 2048; i++) {
result += someMatrixArray[i%64][0] * 0.01;
}
When not accessing someMatrixArray I get 700+ fps. When accessing it, I have 10 fps. Anybody has an idea what could cause this? Could it be a driver issue?
I already tried to unroll the loops (via #pragma optionNV (unroll all)) but that didn't help. I'm using a GTX670 with the latest drivers on windows 7.
Edit:
The generated assembly for the inner loop is:
MAD.F R0.xyz, c[196], {0.0099999998, 0, 0, 0}.x, R0;
resultcan be determined statically without needing to be evaluated in the shader. Why not calculate it on the CPU and pass in the final value ofresultto the shader as a uniform? – Nicolas Louis Guillemot Jun 26 at 23:21result += someMatrixArray[i%64][0] / 100;– Blue Jul 10 at 15:33