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c++avx512

Determine number of AVX-512 FMA units

Is there a possibility to determine the number of AVX-512 FMA units during runtime using C++?
I already have codes to determine if a CPU is capable of AVX-512, but I cannot determine the number of FMA units.

Solution

  • The Intel® 64 and IA-32 Architectures Optimization Reference Manual, February 2022, Chapter 18.21 titled: Servers with a Single FMA Unit contains assembly language source code that identifies the number of AVX-512 FMA Units per core in an AVX-512 capable processor. See Example 18-25. This works by comparing the timing of two functions: one with FMA instructions and another with both FMA and shuffle instructions.

    Intel's optimization manual can be downloaded from: https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html#inpage-nav-8.
    The source code from this manual is available at: https://github.com/intel/optimization-manual