[tests/tsqrt.c] improve coverage

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@12293 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 73 insertions, 1 deletions

diff --git a/tests/tsqrt.c b/tests/tsqrt.c
index 572874824..6d86e5ba2 100644
--- a/tests/tsqrt.c
+++ b/tests/tsqrt.c
@@ -742,17 +742,89 @@ check_underflow (void)
       mpfr_init2 (u, p);
       mpfr_set_ui_2exp (u, 1, mpfr_get_emin () - 1, MPFR_RNDN); /* u = 2 */
       /* for RNDN, since sqrt(2) is closer from 2 than 0, the result is 2 */
+      mpfr_clear_flags ();
       inex = mpfr_sqrt (r, u, MPFR_RNDN);
       MPFR_ASSERTN(inex > 0);
       MPFR_ASSERTN(mpfr_equal_p (r, u));
-      /* for RNDA, the result should be u */
+      MPFR_ASSERTN(mpfr_underflow_p ());
+      /* for RNDA, the result should be u, and there is underflow for p > 1,
+         since for p=1 we have 1 < sqrt(2) < 2, but for p >= 2, sqrt(2) should
+         be rounded to a number <= 1.5, which is representable */
+      mpfr_clear_flags ();
       inex = mpfr_sqrt (r, u, MPFR_RNDA);
       MPFR_ASSERTN(inex > 0);
       MPFR_ASSERTN(mpfr_equal_p (r, u));
+      MPFR_ASSERTN((p == 1 && !mpfr_underflow_p ()) ||
+                   (p != 1 && mpfr_underflow_p ()));
       /* for RNDZ, the result should be +0 */
+      mpfr_clear_flags ();
       inex = mpfr_sqrt (r, u, MPFR_RNDZ);
       MPFR_ASSERTN(inex < 0);
       MPFR_ASSERTN(mpfr_zero_p (r) && mpfr_signbit (r) == 0);
+      MPFR_ASSERTN(mpfr_underflow_p ());
+
+      /* generate an input u such that sqrt(u) < 0.5*2^emin but there is no
+         underflow since sqrt(u) >= pred(0.5*2^emin), thus u >= 2^(2emin-2) */
+      mpfr_set_ui_2exp (u, 1, 2 * mpfr_get_emin () - 2, MPFR_RNDN);
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDN);
+      MPFR_ASSERTN(inex == 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDA);
+      MPFR_ASSERTN(inex == 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDZ);
+      MPFR_ASSERTN(inex == 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+
+      /* next number */
+      mpfr_set_ui_2exp (u, 1, 2 * mpfr_get_emin () - 2, MPFR_RNDN);
+      mpfr_nextabove (u);
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDN);
+      MPFR_ASSERTN(inex < 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDA);
+      MPFR_ASSERTN(inex > 0);
+      mpfr_nextbelow (r);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDZ);
+      MPFR_ASSERTN(inex < 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+
+      /* previous number */
+      mpfr_set_ui_2exp (u, 1, 2 * mpfr_get_emin () - 2, MPFR_RNDN);
+      mpfr_nextbelow (u);
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDN);
+      MPFR_ASSERTN(inex > 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      /* since sqrt(u) is just below the middle between 0.5*2^emin and
+         the previous number (with unbounded exponent range), there is
+         underflow */
+      MPFR_ASSERTN(mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDA);
+      MPFR_ASSERTN(inex > 0);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(!mpfr_underflow_p ());
+      mpfr_clear_flags ();
+      inex = mpfr_sqrt (r, u, MPFR_RNDZ);
+      MPFR_ASSERTN(inex < 0);
+      mpfr_nextabove (r);
+      MPFR_ASSERTN(mpfr_cmp_ui_2exp (r, 1, mpfr_get_emin () - 1) == 0);
+      MPFR_ASSERTN(mpfr_underflow_p ());
+
       mpfr_clear (r);
       mpfr_clear (u);
     }