4 ms·

I don't know about this code in particular but if you're mostly doing math you tend to run out of architectural registers before you achieve the full throughput

• guyomes 3y ago
  That makes sense. I did observe significant speed up using this technic for evaluating a polynomial on several values. I used Hörner algorithm and indeed the number of registers is very small in this case. If the lack of registers is really the bottleneck, a variant might to use both zmm registers for some cumulative sums and ymm registers for some others. In this case the speed up might be less spectacular though. Edit: actually, I just discovered that zmm registers overlap the ymm registers, so the only registers left are the ones from the FPU.
  • gpderetta 3y ago
    AVX512 added 16 more vector registers. Isn't 32 registers enough to unroll by 8?