Attachment 7386 Details for Bug 16521 – test program

test program

test8.c (text/x-c), 1.19 KB, created by Paul Zimmermann on 2014-02-02 20:25:29 UTC

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Creator: Paul Zimmermann

Created: 2014-02-02 20:25:29 UTC

Size: 1.19 KB

patch

obsolete

>#include <stdio.h>
>#include <math.h>
>#include <mpfr.h>
>#include <gnu/libc-version.h>
>#include <fenv.h>
>
>float
>ulp (float x, float y)
>{
>  float z = x - y, t, twoy;
>
>  twoy = y + y;
>  if (twoy != twoy + twoy) /* twoy is finite */
>    t = nextafterf (y, twoy);
>  else /* twoy is +Inf or -Inf */
>    t = nextafter (y, (float) 0);
>  t = y - t;
>  if (t < (float) 0)
>    t = -t;
>  /* now t = ulp(y) */
>  return z / t;
>}
>
>int
>main ()
>{
>  float x = -0x7.e000b8p4;
>  float y, z;
>  mpfr_t t;
>  int inex, runderflow;
>
>  printf("GNU libc version: %s\n", gnu_get_libc_version ());
>  printf("GNU libc release: %s\n", gnu_get_libc_release ());
>  fesetround (FE_UPWARD);
>  feclearexcept (FE_ALL_EXCEPT);
>  y = exp2f (x);
>  runderflow = fetestexcept (FE_UNDERFLOW);
>  mpfr_set_emin (-125 - 24 + 1);
>  mpfr_set_emax (128);
>  mpfr_init2 (t, 24);
>  mpfr_set_flt (t, x, MPFR_RNDN); /* exact */
>  inex = mpfr_exp2 (t, t, MPFR_RNDU);
>  inex = mpfr_subnormalize (t, inex, MPFR_RNDU);
>  z = mpfr_get_flt (t, MPFR_RNDN); /* exact */
>  printf ("x=%a (%.9e)\n", x, x);
>  printf ("libc: exp2f(x)=%a (%.9e) underflow=%d\n", y, y, runderflow);
>  printf ("mpfr: exp2f(x)=%a (%.9e)\n", z, z);
>  printf ("ulp difference: %f\n", ulp (y, z));
>  return 0;
>}

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Attachments on bug 16521: 7386