[src/sum.c] Fixed bugs in mpfr_sum, which could return wrong results

  when not all the numbers have the same precision. A side effect is
  that this can make mpfr_sum much slower and/or take much more memory
  in some of such cases with the same program; this is normal and
  cannot easily be avoided with the current algorithm.
  Note: The full rewrite currently in the trunk has not been merged
  because this would not be a simple patch (and it is still incomplete
  when a number is reused as the output).
[src/mpfr-impl.h] Updated the prototype of mpfr_sum_sort.
  Note: Since this function is used only internally and by the tests,
  this does not break the ABI. However the old and new tsum tests are
  source & binary incompatible.
[tests/tsum.c] Updated the use of mpfr_sum_sort. Added a testcase.
(merged changesets r8697,8699,8701,8851 from the trunk)

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/3.1@10083 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 38 insertions, 1 deletions

diff --git a/tests/tsum.c b/tests/tsum.c
index 5d9c8b598..38ebf52e3 100644
--- a/tests/tsum.c
+++ b/tests/tsum.c
@@ -126,6 +126,7 @@ test_sort (mpfr_prec_t f, unsigned long n)
   mpfr_ptr *tabtmp;
   mpfr_srcptr *perm;
   unsigned long i;
+  mpfr_prec_t prec = MPFR_PREC_MIN;
 
   /* Init stuff */
   tab = (mpfr_t *) (*__gmp_allocate_func) (n * sizeof (mpfr_t));
@@ -140,7 +141,7 @@ test_sort (mpfr_prec_t f, unsigned long n)
       tabtmp[i] = tab[i];
     }
 
-  mpfr_sum_sort ((mpfr_srcptr *)tabtmp, n, perm);
+  mpfr_sum_sort ((mpfr_srcptr *)tabtmp, n, perm, &prec);
 
   if (check_is_sorted (n, perm) == 0)
     {
@@ -300,6 +301,41 @@ void check_special (void)
   mpfr_clears (tab[0], tab[1], tab[2], r, (mpfr_ptr) 0);
 }
 
+/* bug reported by Joseph S. Myers on 2013-10-27
+   https://sympa.inria.fr/sympa/arc/mpfr/2013-10/msg00015.html */
+static void
+bug20131027 (void)
+{
+  mpfr_t r, t[4];
+  mpfr_ptr p[4];
+  char *s[4] = {
+    "0x1p1000",
+    "-0x0.fffffffffffff80000000000000001p1000",
+    "-0x1p947",
+    "0x1p880"
+  };
+  int i;
+
+  mpfr_init2 (r, 53);
+  for (i = 0; i < 4; i++)
+    {
+      mpfr_init2 (t[i], i == 0 ? 53 : 1000);
+      mpfr_set_str (t[i], s[i], 0, MPFR_RNDN);
+      p[i] = t[i];
+    }
+  mpfr_sum (r, p, 4, MPFR_RNDN);
+
+  if (MPFR_NOTZERO (r))
+    {
+      printf ("mpfr_sum incorrect in bug20131027: expected 0, got\n");
+      mpfr_dump (r);
+      exit (1);
+    }
+
+  for (i = 0; i < 4; i++)
+    mpfr_clear (t[i]);
+  mpfr_clear (r);
+}
 
 int
 main (void)
@@ -310,6 +346,7 @@ main (void)
   tests_start_mpfr ();
 
   check_special ();
+  bug20131027 ();
   test_sort (1764, 1026);
   for (p = 2 ; p < 444 ; p += 17)
     for (n = 2 ; n < 1026 ; n += 42 + p)