[tests/tests.c] Revert a change done in r13783 for function bad_cases():

  no longer fail if a generated value does not correspond to a bad case.
  But fail if the MPFR_CHECK_BADCASES environment variable is defined
  and too few bad cases are generated (less than 90%).
[doc/README.dev] Document MPFR_CHECK_BADCASES.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@13788 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 27 insertions, 8 deletions

diff --git a/doc/README.dev b/doc/README.dev
index 1ee7ee641..06518f9e8 100644
--- a/doc/README.dev
+++ b/doc/README.dev
@@ -340,7 +340,7 @@ To make a release (for the MPFR team):
 
      Also test with different environment variables set
      (GMP_CHECK_RANDOMIZE, MPFR_CHECK_LIBC_PRINTF, MPFR_CHECK_LARGEMEM,
-     MPFR_SUSPICIOUS_OVERFLOW, MPFR_CHECK_LOCALES).
+     MPFR_SUSPICIOUS_OVERFLOW, MPFR_CHECK_LOCALES, MPFR_CHECK_BADCASES).
 
      Check there is no branch misprediction due to wrong MPFR_LIKELY or
      MPFR_UNLIKELY statements. For that test, configure with
@@ -580,6 +580,10 @@ Environment variables that affect the tests:
                         sure that needed locales are properly installed
                         and tested.
 
++ MPFR_CHECK_BADCASES:  Fail if function bad_cases generates too many
+                        cases for which f(f^{-1}(x)) ≠ x, due to a poor
+                        choice of the parameters.
+
 + MPFR_DEBUG_BADCASES:  For debugging (see tests.c, function bad_cases).
 
 + MPFR_SUSPICIOUS_OVERFLOW:
diff --git a/tests/tests.c b/tests/tests.c
index a82a44a54..a27f2109f 100644
--- a/tests/tests.c
+++ b/tests/tests.c
@@ -987,7 +987,7 @@ bad_cases (int (*fct)(FLIST), int (*inv)(FLIST), const char *name,
 {
   mpfr_t x, y, z;
   char *dbgenv;
-  int i, dbg;
+  int cnt = 0, i, dbg;
   mpfr_exp_t old_emin, old_emax;
 
   old_emin = mpfr_get_emin ();
@@ -1068,12 +1068,16 @@ bad_cases (int (*fct)(FLIST), int (*inv)(FLIST), const char *name,
           if (mpfr_nanflag_p () || mpfr_overflow_p () || mpfr_underflow_p ()
               || ! mpfr_equal_p (z, y))
             {
-              printf ("bad_cases: inverse doesn't match for %s\ny = ", name);
-              mpfr_out_str (stdout, 16, 0, y, MPFR_RNDN);
-              printf ("\nz = ");
-              mpfr_out_str (stdout, 16, 0, z, MPFR_RNDN);
-              printf ("\n");
-              exit (1);
+              if (dbg)
+                {
+                  printf ("bad_cases: inverse doesn't match for %s\ny = ",
+                          name);
+                  mpfr_out_str (stdout, 16, 0, y, MPFR_RNDN);
+                  printf ("\nz = ");
+                  mpfr_out_str (stdout, 16, 0, z, MPFR_RNDN);
+                  printf ("\n");
+                }
+              goto next_i;
             }
         }
       while (inex == 0);
@@ -1104,6 +1108,7 @@ bad_cases (int (*fct)(FLIST), int (*inv)(FLIST), const char *name,
         }
       /* Note: y is now the expected result rounded toward zero. */
       test5rm (fct, x, y, z, MPFR_RNDZ, sb, name);
+      cnt++;
     next_i:
       /* In case the exponent range has been changed by
          tests_default_random()... */
@@ -1111,6 +1116,16 @@ bad_cases (int (*fct)(FLIST), int (*inv)(FLIST), const char *name,
       mpfr_set_emax (old_emax);
     }
   mpfr_clears (x, y, z, (mpfr_ptr) 0);
+
+  if (dbg)
+    printf ("bad_cases: %d bad cases over %d generated values\n", cnt, n);
+
+  if (getenv ("MPFR_CHECK_BADCASES") && n - cnt > n/10)
+    {
+      printf ("bad_cases: too few bad cases (%d over %d generated values)\n",
+              cnt, n);
+      exit (1);
+    }
 }
 
 void