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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - Invalid subgroupSize for Intel GPU"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108875#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - Invalid subgroupSize for Intel GPU"
href="https://bugs.freedesktop.org/show_bug.cgi?id=108875">bug 108875</a>
from <span class="vcard"><a class="email" href="mailto:frustumo@gmail.com" title="Alexander <frustumo@gmail.com>"> <span class="fn">Alexander</span></a>
</span></b>
<pre>I tried to run a simple compute shader to test subgroup instructions:
layout(local_size_x = subgroupSize) in;
layout(std430, binding = 0) writeonly buffer output_buffer { uint output[]; };
void main() {
uint id = gl_GlobalInvocationID.x;
output[id] = subgroupAdd(id);
}
The output on Intel is:
120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120
376 376 376 376 376 376 376 376 376 376 376 376 376 376 376 376
632 632 632 632 632 632 632 632 632 632 632 632 632 632 632 632
888 888 888 888 888 888 888 888 888 888 888 888 888 888 888 888
The real subgroup size is 16 on Intel (32 on NVidia and 64 on AMD hardware).
PS: It's interesting that subgroup size under Direct3D12 (DXIL shader) equals
to 8.</pre>
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