[src/zeta_ui.c] Fixed zeta(0) in reduced exponent range.

[tests/tzeta_ui.c] Added testcase.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@9518 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 56 insertions, 7 deletions

diff --git a/src/zeta_ui.c b/src/zeta_ui.c
index c8155936b..7bd9736cd 100644
--- a/src/zeta_ui.c
+++ b/src/zeta_ui.c
@@ -30,10 +30,7 @@ mpfr_zeta_ui (mpfr_ptr z, unsigned long m, mpfr_rnd_t r)
 
   if (m == 0)
     {
-      mpfr_set_ui (z, 1, r);
-      mpfr_div_2ui (z, z, 1, r);
-      MPFR_CHANGE_SIGN (z);
-      MPFR_RET (0);
+      return mpfr_set_si_2exp (z, -1, -1, r);
     }
   else if (m == 1)
     {
diff --git a/tests/tzeta_ui.c b/tests/tzeta_ui.c
index fbbbf287e..589227c97 100644
--- a/tests/tzeta_ui.c
+++ b/tests/tzeta_ui.c
@@ -33,9 +33,15 @@ main (int argc, char *argv[])
   mpfr_t x, y, z, t;
   unsigned long n;
   int inex;
+  mpfr_exp_t emin, emax;
+  mpfr_flags_t flags, ex_flags;
+  int i;
 
   tests_start_mpfr ();
 
+  emin = mpfr_get_emin ();
+  emax = mpfr_get_emax ();
+
   mpfr_init (x);
   mpfr_init (y);
   mpfr_init (z);
@@ -63,10 +69,56 @@ main (int argc, char *argv[])
       exit (1);
     }
 
-  mpfr_clear_divby0 ();
+  mpfr_clear_flags ();
   inex = mpfr_zeta_ui (x, 0, MPFR_RNDN);
-  MPFR_ASSERTN (inex == 0 && mpfr_cmp_si_2exp (x, -1, -1) == 0
-                && !mpfr_divby0_p ());
+  flags = __gmpfr_flags;
+  MPFR_ASSERTN (inex == 0 && mpfr_cmp_si_2exp (x, -1, -1) == 0 && flags == 0);
+
+  for (i = -2; i <= 2; i += 2)
+    {
+      int ex_inex, err;
+      char *s;
+
+      set_emin (i);
+      set_emax (i);
+      mpfr_clear_flags ();
+      inex = mpfr_zeta_ui (x, 0, MPFR_RNDN);
+      flags = __gmpfr_flags;
+      set_emin (emin);
+      set_emax (emax);
+      if (i < 0)
+        {
+          s = "-@Inf@";
+          ex_inex = -1;
+          ex_flags = MPFR_FLAGS_OVERFLOW | MPFR_FLAGS_INEXACT;
+          err = !(mpfr_inf_p (x) && MPFR_IS_NEG (x));
+        }
+      else if (i > 0)
+        {
+          s = "-0";
+          ex_inex = 1;
+          ex_flags = MPFR_FLAGS_UNDERFLOW | MPFR_FLAGS_INEXACT;
+          err = !(mpfr_zero_p (x) && MPFR_IS_NEG (x));
+        }
+      else
+        {
+          s = "-1/2";
+          ex_inex = 0;
+          ex_flags = 0;
+          err = mpfr_cmp_si_2exp (x, -1, -1) != 0;
+        }
+      if (err || ! SAME_SIGN (inex, ex_inex) || flags != ex_flags)
+        {
+          printf ("Failure for zeta(0) in exponent range [%d,%d]\n", i, i);
+          printf ("Expected %s, sign(inex) = %d, flags =", s, ex_inex);
+          flags_out (ex_flags);
+          printf ("Got      ");
+          mpfr_dump (x);
+          printf ("with inex = %d, flags =", inex);
+          flags_out (flags);
+          exit (1);
+        }
+    }
 
   mpfr_clear_divby0 ();
   inex = mpfr_zeta_ui (x, 1, MPFR_RNDN);