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Mutithreading R2C problem #263

Open pidanself opened 2 years ago

pidanself commented 2 years ago

8 threads R2C with simd is slower than 4 threads R2C with simd.

Eviroment:
  CPU: intel i9 with 8 cores
  OS: macos
  compiler: macos gcc
  version: fftw-3.3.10
  ISA: AVX2
  threads: --enable-threads
  precision: single
  test way: ./bench -r 100 -v2 -owisdom -onthreads=4/8 60000/r60000

Below is my test data: <html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:x="urn:schemas-microsoft-com:office:excel" xmlns="http://www.w3.org/TR/REC-html40">

size | 4 threads | 8 threads | speedup -- | -- | -- | -- r2c:60000 | 29000 mflops| 25000 mflops| 0.86206897 c2c:60000 | 31000 mflops| 41000 mflops| 1.32258065

C2C with 8 threads is faster than 4 threads. R2C with 8 threads is slower than 4 threads.

From above data, we can find R2C computations may have some problems.

I will test more datas to display this problem.

I guess fftw compute r2c through thransform r2c problems to c2c problems.If C2C is normal, R2C should be normal.

Are the test results normal? Or somthing wrong?