Fuzzing programs is really a CPU task, although it can usually be horizontally scaled across multiple boxes.
Its quite possible that someone figures out an x86 emulator on GPUs that fuzzes register values, similar to AVX512 fuzzing. https://gamozolabs.github.io/fuzzing/2018/10/14/vectorized_e...
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Fuzzing is unique in that 99% of code probably traverses the same set of if-statements or branches. Whenever code significantly diverges (usually defined by Fuzzers as a significantly different instruction-pointer path of some kind), you've successfully fuzzed a new result.
Fuzzers... strangely enough... are programs I'd expect to run pretty well on GPUs or SIMD. If enough R&D research effort were put into it.