[tests/tgeneric.c] Tests in a reduced exponent range:

  * Do several overflow/underflow tests instead of 1, and this for each
    precision. This allows one to detect 2 bugs (fixed in the trunk)
    that did not handle reduced exponent ranges correctly:
    - in mpfr_ai, making tai fail;
    - in mpfr_lgamma, making tlgamma hang with a 32-bit ABI.
  * Added some comments.
(merged changesets r12087-12088 from the trunk)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/4.0@12093 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 25 insertions, 8 deletions

diff --git a/tests/tgeneric.c b/tests/tgeneric.c
index 2e3c54098..942987498 100644
--- a/tests/tgeneric.c
+++ b/tests/tgeneric.c
@@ -157,7 +157,6 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
   int inexact, compare, compare2;
   unsigned int n;
   unsigned long ctrt = 0, ctrn = 0;
-  int test_of = 1, test_uf = 1;
   mpfr_exp_t old_emin, old_emax;
 
   old_emin = mpfr_get_emin ();
@@ -171,6 +170,12 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
   /* generic test */
   for (prec = p0; prec <= p1; prec++)
     {
+      /* Number of overflow/underflow tests for each precision.
+         Since MPFR uses several algorithms and there may also be
+         early overflow/underflow detection, several tests may be
+         needed to detect a bug. */
+      int test_of = 3, test_uf = 3;
+
       mpfr_set_prec (z, prec);
       mpfr_set_prec (t, prec);
       yprec = prec + 10;
@@ -423,11 +428,15 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
 #endif
             if (MPFR_IS_PURE_FP (y))
               {
-                e = MPFR_GET_EXP (y);
-                if (test_of && e - 1 >= emax)
+                e = MPFR_GET_EXP (y);  /* exponent of the result */
+
+                if (test_of > 0 && e - 1 >= emax)  /* overflow test */
                   {
                     mpfr_flags_t ex_flags;
 
+                    /* Exponent e of the result > exponents of the inputs;
+                       let's set emax to e - 1, so that one should get an
+                       overflow. */
                     mpfr_set_emax (e - 1);
 #ifdef MPFR_DEBUG_TGENERIC
                     printf ("tgeneric: overflow test (emax = %"
@@ -481,12 +490,16 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
                         mpfr_dump (w);
                         exit (1);
                       }
-                    test_of = 0;  /* Overflow is tested only once. */
+                    test_of--;
                   }
-                if (test_uf && e + 1 <= emin)
+
+                if (test_uf > 0 && e + 1 <= emin)  /* underflow test */
                   {
                     mpfr_flags_t ex_flags;
 
+                    /* Exponent e of the result < exponents of the inputs;
+                       let's set emin to e + 1, so that one should get an
+                       underflow. */
                     mpfr_set_emin (e + 1);
 #ifdef MPFR_DEBUG_TGENERIC
                     printf ("tgeneric: underflow test (emin = %"
@@ -540,15 +553,18 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
                         mpfr_dump (w);
                         exit (1);
                       }
-                    test_uf = 0;  /* Underflow is tested only once. */
+                    test_uf--;
                   }
+
                 if (e < emin)
                   emin = e;
                 if (e > emax)
                   emax = e;
-              }
+              }  /* MPFR_IS_PURE_FP (y) */
+
             if (emin > emax)
               emin = emax;  /* case where all values are singular */
+
             /* Consistency test in a reduced exponent range. Doing it
                for the first 10 samples and for prec == p1 (which has
                some special cases) should be sufficient. */
@@ -609,8 +625,9 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
                     exit (1);
                   }
               }
+
             __gmpfr_flags = oldflags;  /* restore the flags */
-          }
+          }  /* tests in a reduced exponent range */
 
           if (MPFR_IS_SINGULAR (y))
             {