[tests/tsub.c] More tests in bug20180216.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@12257 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 25 insertions, 16 deletions

diff --git a/tests/tsub.c b/tests/tsub.c
index 97f2ef2ee..dd1a1401b 100644
--- a/tests/tsub.c
+++ b/tests/tsub.c
@@ -981,27 +981,36 @@ static void
 bug20180216 (void)
 {
   mpfr_t x, y, z1, z2;
-  int r, p, inex;
+  int r, p, d, inex;
 
-  for (p = 4; p <= 4 + 4 * GMP_NUMB_BITS; p++)
+  for (p = 3; p <= 3 + 4 * GMP_NUMB_BITS; p++)
     {
       mpfr_inits2 (p, x, y, z1, z2, (mpfr_ptr) 0);
-      mpfr_set_ui (x, 5, MPFR_RNDN);
-      mpfr_nextabove (x);
-      mpfr_sub_ui (y, x, 4, MPFR_RNDN);
-      mpfr_set_ui (z1, 4, MPFR_RNDN);
-      RND_LOOP (r)
+      for (d = 1; d <= p-2; d++)
         {
-          inex = test_sub (z2, x, y, (mpfr_rnd_t) r);
-          if (! mpfr_equal_p (z1, z2) || inex != 0)
+          inex = mpfr_set_ui_2exp (z1, 1, d, MPFR_RNDN);  /* z1 = 2^d */
+          MPFR_ASSERTN (inex == 0);
+          inex = mpfr_add_ui (x, z1, 1, MPFR_RNDN);
+          MPFR_ASSERTN (inex == 0);
+          mpfr_nextabove (x);  /* x = 2^d + 1 + epsilon */
+          inex = mpfr_sub (y, x, z1, MPFR_RNDN);  /* y = 1 + epsilon */
+          MPFR_ASSERTN (inex == 0);
+          inex = mpfr_add (z2, y, z1, MPFR_RNDN);
+          MPFR_ASSERTN (inex == 0);
+          MPFR_ASSERTN (mpfr_equal_p (z2, x));  /* consistency check */
+          RND_LOOP (r)
             {
-              printf ("Error in bug20180216 in precision %d, %s\n",
-                      p, mpfr_print_rnd_mode ((mpfr_rnd_t) r));
-              printf ("expected "); mpfr_dump (z1);
-              printf ("  with inex = 0\n");
-              printf ("got      "); mpfr_dump (z2);
-              printf ("  with inex = %d\n", inex);
-              exit (1);
+              inex = test_sub (z2, x, y, (mpfr_rnd_t) r);
+              if (! mpfr_equal_p (z1, z2) || inex != 0)
+                {
+                  printf ("Error in bug20180216 with p=%d, d=%d, %s\n",
+                          p, d, mpfr_print_rnd_mode ((mpfr_rnd_t) r));
+                  printf ("expected "); mpfr_dump (z1);
+                  printf ("  with inex = 0\n");
+                  printf ("got      "); mpfr_dump (z2);
+                  printf ("  with inex = %d\n", inex);
+                  exit (1);
+                }
             }
         }
       mpfr_clears (x, y, z1, z2, (mpfr_ptr) 0);