[tests/tgeneric.c] Improved the generic tests in order to trigger the

mpfr_jn bug found by Fredrik Johansson (r9841) and potential similar
bugs: For half cases, the precision of the inputs was modified to be
smaller than the base precision (for the result). Here, this rule is
changed so that if the base precision is small (< 16), then the
precision of the inputs is chosen to be significantly *larger* than
the base precision in general.
Note: With this improvement, both tj0 and tj1 fail in r9840.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@9848 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 6 insertions, 1 deletions

diff --git a/tests/tgeneric.c b/tests/tgeneric.c
index 99f1a675c..93c386146 100644
--- a/tests/tgeneric.c
+++ b/tests/tgeneric.c
@@ -176,7 +176,12 @@ test_generic (mpfr_prec_t p0, mpfr_prec_t p1, unsigned int nmax)
           xprec = prec;
           if (randlimb () & 1)
             {
-              xprec *= (double) randlimb () / MPFR_LIMB_MAX;
+              /* In half cases, modify the precision of the inputs:
+                 If the base precision (for the result) is small,
+                 take a larger input precision in general, else
+                 take a smaller precision. */
+              xprec *= (prec < 16 ? 256.0 : 1.0) *
+                (double) randlimb () / MPFR_LIMB_MAX;
               if (xprec < MPFR_PREC_MIN)
                 xprec = MPFR_PREC_MIN;
             }