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> GPUs do not actually have control flow. Wrong. Let's look at the instriction set of the AMD GCN3 ISA: > http://gpuopen.com/compute-product/amd-gcn3-isa-arch

by wolfgke 10y ago

> GPUs do not actually have control flow. Wrong. Let's look at the instriction set of the AMD GCN3 ISA: > http://gpuopen.com/compute-product/amd-gcn3-isa-architecture-manual/ http://gpuopen.com/compute-product/amd-gcn3-isa-architecture... which links to > http://32ipi028l5q82yhj72224m8j.wpengine.netdna-cdn.com/wp-content/uploads/2016/08/AMD_GCN3_Instruction_Set_Architecture_rev1.1.pdf http://32ipi028l5q82yhj72224m8j.wpengine.netdna-cdn.com/wp-c... which even has a whole chapter about control flow: "Chapter 4 Program Control Flow".

deleted 10y ago
[deleted]
andars 10y ago
> Wrong. I'd say it's more like "not quite". ~10 years ago, the statement was pretty much correct. GPUs were entirely SIMD, so they couldn't truly branch, but could fake it with predication. Longer branches would involve executing both branches on every thread and only committing the results of the active branch. Modern GPUs can do much better, since individual warps/wavefronts can truly diverge. Within warps, however, it's still a bit of a mess.
- wolfgke 10y ago
  > ~10 years ago, the statement was pretty much correct. If one looks at the capabilities of CPUs from 10 years ago, one can easily justify similar completely outdated statements for CPUs.