Environment variables control the disabling of certain explicit SIMD optimizations.
x64 options:
ATEN_CPU_CAPABILITY=avx2 # Force AVX2 codepaths to be used
ATEN_CPU_CAPABILITY=avx # Force AVX codepaths to be used
ATEN_CPU_CAPABILITY=default # Use oldest supported vector instruction set
ppc64le options:
TH_NO_VSX=1 # disable VSX codepaths