octave_rand::scalar() speed

[Steve C. Thompson]

Hello Group,

I'm finding octave_rand::scalar() to be slow.  Any idea why the
following code takes 10 seconds to run?


#include <octave/oct.h>
#include <octave/oct-rand.h>

DEFUN_DLD (slow, args, ,
  "This is slow")
{
  octave_value_list retval;

  double a;
  double b;
  double c = 0;

  while (c < 1e7)
    {
      a = octave_rand::scalar();
      b = octave_rand::scalar();
      a = octave_rand::scalar();
      b = octave_rand::scalar();
      a = octave_rand::scalar();
      b = octave_rand::scalar();
      c++;
    }

  retval(0) = a;
  retval(1) = b;
  retval(2) = c;

  return retval;
}

If I replace octave_rand::scalar() with rand() it runs faster, but the
algorithm is rand() is slower than MT.

Thanks,
Steve



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