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• #8597 S_x96x_S addikt

  Új Válasz 2023-02-08 12:58:57 #8597

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  S_x96x_S

  addikt

  A ZEN4-es szoftveres támogatás elég lassú ....
  de azért halad ...

  GCC 13 Now Enables 512-bit Vector For AMD Zen 4 Tuning
  https://www.phoronix.com/news/GCC-13-Zen-4-Znver4-512b-Vector

  Enable 512 bit vector for zen4
  
  While internally 512 registers are splits into two 256 halves, 512 bit vectors
  reduces number of instructions to retire and has chance to improve paralelism.
  There are few tsvc benchmarks that improves significantly:
  
  runtime
  benchmark 256bit 512bit
  s2275 48.57 20.67 -58%
  s311 32.29 16.06 -50%
  s312 32.30 16.07 -50%
  vsumr 32.30 16.07 -50%
  s314 10.77 5.42 -50%
  s313 21.52 10.85 -50%
  vdotr 43.05 21.69 -50%
  s316 10.80 5.64 -48%
  s235 61.72 33.91 -45%
  s161 15.91 9.95 -38%
  s3251 32.13 20.31 -36%
  
  And there are no benchmarks with off-noise regression. The basic matrix
  multiplication loop improves by 32%. It is also expected that 512 bit
  vectors are more power effecient (I can't masure that).
  
  The down side is that loops with low trip counts may get slower when the
  unvectorized prologue and epilogue is hit more often. With SPECfp this
  problem happens with x264 (12% regression) and bwaves (6% regression)
  and this is tracked in
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108410
  and will need more work on vectorizer to support masked epilogues.
  
  After some additional testing it seems that using 512 bit vectors by
  default is now overall better choice.

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