[Bug fortran/29549] matmul slow for complex matrices

["jb at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from jb at gcc dot gnu dot org  2006-11-04 21:24 -------
Well, redoing the C benchmark above to use 1d arrays and manual index
calculations, the results are now essentially the same as for the Fortran
version. And a commercial compiler produces about the same results for the
Fortran version as gfortran, which means the reason for our poor complex matmul
performance lies elsewhere.

#include <stdio.h>
#include <stdlib.h>
#include <complex.h>
#include <sys/time.h>
#include <time.h>

int main(void)
{
  int n = 300;
  complex float *a, *b, *c;
  int i, j, k, tc;
  a = malloc (n*n * sizeof (*a));
  b = malloc (n*n * sizeof (*b));
  c = malloc (n*n * sizeof (*c));
  struct timeval tv, tv2;
  float res;
  FILE *fp;

  tc = 0;
  for (i = 0; i < n*n; i++)
    {
      a[i] = i*10.0 + 100.0*I;
      b[i] = 1.0 + 42.0*I;
      c[i] = 0.0 + 0.0*I;
    }

  gettimeofday (&tv, NULL);

  for (i = 0; i < n; i++)
    {
      for (j = 0; j < n; j++)
        {
          c[i*n + j] = 0.0 + 0.0*I;
          for (k = 0; k < n; k++)
            {
              c[i*n + j] = c[i*n + j] + a[i*n + k] * b[k*n + j];
              tc++;
            }
        }
    }
  gettimeofday (&tv2, NULL);
  res = tv2.tv_sec - tv.tv_sec + (tv2.tv_usec - tv.tv_usec) / 1000000.0;
  printf ("gemm time: %f\n", res);
  fp = fopen ("c-matrix", "w");
  for (i = 0; i < n; i++)
    {
      for (j = 0; j<n; j++)
        {
          fprintf (fp, "%f ", c[i*n + j]);
        }
      fprintf (fp, "\n");
    }
  fclose (fp);
  printf ("trip count: %i\n", tc);
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29549