mapleFU commented on issue #43687:
URL: https://github.com/apache/arrow/issues/43687#issuecomment-2289531460
```
/// \brief Indicates the level of SIMD instruction support in the host CPU
is
/// required to use the function. The intention is for functions to be
able to
/// contain multiple kernels with the same signature but different levels
of SIMD,
/// so that the most optimized kernel supported on a host's processor can
be chosen.
SimdLevel::type simd_level = SimdLevel::NONE;
```
I think this is the "exact" simd-level it's using. Since a AVX2 machine
execute a code with higher level is not wise
besides, from `DispatchExactImpl`, this would cause override of avx2 in the
`kernel_matches`. I don't think this is expected?
```C++
template <typename KernelType>
const KernelType* DispatchExactImpl(const std::vector<KernelType*>& kernels,
const std::vector<TypeHolder>& values) {
const KernelType* kernel_matches[SimdLevel::MAX] = {nullptr};
// Validate arity
for (const auto& kernel : kernels) {
if (kernel->signature->MatchesInputs(values)) {
kernel_matches[kernel->simd_level] = kernel;
}
}
#if defined(ARROW_HAVE_RUNTIME_AVX512) || defined(ARROW_HAVE_RUNTIME_AVX2)
auto cpu_info = arrow::internal::CpuInfo::GetInstance();
#endif
#if defined(ARROW_HAVE_RUNTIME_AVX512)
if (cpu_info->IsSupported(arrow::internal::CpuInfo::AVX512)) {
if (kernel_matches[SimdLevel::AVX512]) {
return kernel_matches[SimdLevel::AVX512];
}
}
#endif
```
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