Re: float formating with xx.00

/*
**
** Not a surprise, to them that knows:
**
*/
#include <stdio.h>
#include <stdlib.h>

#define A_LEN 500

static float foo[A_LEN];

static double bar[A_LEN];

int
main (void)
{
  long i;
  double d;
  float f;
  for (i = 0; i < A_LEN; i++)
    {
      d = rand () / (rand () + 1.0);
      d *= d;
      if (rand () % 2)
        d = -d;
      foo[i] = (float) d;
      bar[i] = d;
    }
  f = 0;
  d = 0;
  for (i = 0; i < A_LEN; i++)
    {
      f += foo[i];
      d += bar[i];
    }
  printf ("forward  float  sum = %.20f\n", f);
  printf ("forward  double sum = %.20f\n", d);
  f = 0;
  d = 0;
  for (i = A_LEN - 1; i >= 0; i--)
    {
      f += foo[i];
      d += bar[i];
    }
  printf ("backward float  sum = %.20f\n", f);
  printf ("backward double sum = %.20f\n", d);
  return 0;
}
/*

OpenVMS VAX:

$ run foo
forward  float  sum = -6724682.50000000000000000000
forward  double sum = -6724682.13690311496610000000
backward float  sum = -6724679.50000000000000000000
backward double sum = -6724682.13690311496610000000

OpenVMS Alpha:
$ run foo
forward  float  sum = -6724682.50000000000000000000
forward  double sum = -6724682.13690311090000000000
backward float  sum = -6724679.50000000000000000000
backward double sum = -6724682.13690311370000000000
$

GCC on AMD Athlon:
$ ./a
forward  float  sum = -56051.43860578643943881616
forward  double sum = -56051.43626179593411507085
backward float  sum = -56051.43860578643943881616
backward double sum = -56051.43626179593411507085

MS VC++ 6 on AMD Athlon with /Ox flag:

C:\tmp>foo
forward  float  sum = 545785.98050410976000000000
forward  double sum = 545786.01145155274000000000
backward float  sum = 545785.98050410964000000000
backward double sum = 545786.01145155251000000000

MS VC++ 6 on AMD Athlon with /Op flag (forces memory storage):

C:\tmp>foo
forward  float  sum = 545785.93750000000000000000
forward  double sum = 545786.01145155274000000000
backward float  sum = 545785.56250000000000000000
backward double sum = 545786.01145155251000000000

*/