[C++] What's the difference between ARROW_SIMD_LEVEL and ARROW_RUNTIME_SIMD_LEVEL #40333
Description
Describe the usage question you have. Please include as many useful details as possible.
In Arrow, we have two SIMD flag in CMake listed below:
define_option_string(ARROW_SIMD_LEVEL
"Compile-time SIMD optimization level"
"DEFAULT" # default to SSE4_2 on x86, NEON on Arm, NONE otherwise
"NONE"
"SSE4_2"
"AVX2"
"AVX512"
"NEON"
"SVE" # size agnostic SVE
"SVE128" # fixed size SVE
"SVE256" # "
"SVE512" # "
"DEFAULT")
define_option_string(ARROW_RUNTIME_SIMD_LEVEL
"Max runtime SIMD optimization level"
"MAX" # default to max supported by compiler
"NONE"
"SSE4_2"
"AVX2"
"AVX512"
"MAX")They're added in the two patches:
However, ARROW_RUNTIME_SIMD_LEVEL would also be checked in compile time. So, what's the difference between these two flags? Or do I misunderstand the meaning of "runtime" here(I mean dynamicly checking it when runing the program)?
Component(s)
C++