Merged the latest changes from the trunk.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/branches/ubf@10439 280ebfd0-de03-0410-8827-d642c229c3f4

6 files changed, 60 insertions, 18 deletions

diff --git a/TODO b/TODO
index ce692f9f3..39fe6d47e 100644
--- a/TODO
+++ b/TODO
@@ -451,6 +451,24 @@ Table of contents:
   * In debug mode, MPFR would check that the result is exact
     (i.e. that the ternary value is 0).
 
+- new "rounding mode" MPFR_RNDF (faithful rounding)?
+  This is not really a rounding mode since it is non-deterministic. The
+  goal is to avoid the Table Maker's Dilemma in internal computations.
+  The definition of faithful rounding of a real number x is: return either
+  RNDD(x) or RNDU(x). This means that if x is exactly representable, one
+  returns x exactly. In MPFR, the ternary value should be unspecified for
+  efficiency reasons.
+  Note: One typically implements faithful rounding by computing an
+  approximation to the result with some adequately chosen error bound,
+  then by rounding this approximation to nearest.
+  Concerning the choice of the error bound, if the result x is equal to
+  1 + t, where t is a very small positive number, then the error bound
+  needs to be at most ulp(x)/4 + t. Since t can be arbitrarily small,
+  the error bound needs to be at most ulp(x)/4. And this error bound
+  is sufficient in all cases. Note that with the even rounding rule or
+  rounding away from zero, it is not needed to relax the condition when
+  x is exactly representable.
+
 - add tests of the ternary value for constants
 
 - When doing Extensive Check (--enable-assert=full), since all the
diff --git a/src/add1.c b/src/add1.c
index 37284a9b1..4e210390e 100644
--- a/src/add1.c
+++ b/src/add1.c
@@ -248,11 +248,7 @@ mpfr_add1 (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mpfr_rnd_t rnd_mode)
           if (fb > 0)
             {
               if (bb != MPFR_LIMB_MAX)
-                {
-                  fb = 1; /* c hasn't been taken into account
-                             ==> sticky bit != 0 */
-                  goto rounding;
-                }
+                goto rounding;
             }
           else /* fb not initialized yet */
             {
diff --git a/src/fits_intmax.c b/src/fits_intmax.c
index 423ed1b14..0f738c2f7 100644
--- a/src/fits_intmax.c
+++ b/src/fits_intmax.c
@@ -41,7 +41,7 @@ mpfr_fits_intmax_p (mpfr_srcptr f, mpfr_rnd_t rnd)
   int res;
 
   if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
-    /* Zero always fit */
+    /* Zero always fits */
     return MPFR_IS_ZERO (f) ? 1 : 0;
 
   /* now it fits if either
diff --git a/src/fits_s.h b/src/fits_s.h
index c639fbb12..93f970b2a 100644
--- a/src/fits_s.h
+++ b/src/fits_s.h
@@ -37,7 +37,7 @@ FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
   int res;
 
   if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
-    /* Zero always fit */
+    /* Zero always fits */
     return MPFR_IS_ZERO (f) ? 1 : 0;
 
   /* now it fits if either
diff --git a/src/set_float128.c b/src/set_float128.c
index 98e47449b..8aa11bd43 100644
--- a/src/set_float128.c
+++ b/src/set_float128.c
@@ -28,6 +28,9 @@ http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
 
 #ifdef MPFR_WANT_FLOAT128
 
+/* The q suffix is a GNU C extension, but so is __float128. */
+#define MPFR_FLOAT128_MAX 0x1.ffffffffffffffffffffffffffffp+16383q
+
 int
 mpfr_set_float128 (mpfr_ptr r, __float128 d, mpfr_rnd_t rnd_mode)
 {
@@ -44,14 +47,16 @@ mpfr_set_float128 (mpfr_ptr r, __float128 d, mpfr_rnd_t rnd_mode)
     }
 
   /* Check for INF */
-  if (MPFR_UNLIKELY (d == ((__float128) 1.0 / (__float128) 0.0)))
+  if (MPFR_UNLIKELY (d > MPFR_FLOAT128_MAX))
     {
-      mpfr_set_inf (r, 1);
+      MPFR_SET_INF (r);
+      MPFR_SET_POS (r);
       return 0;
     }
-  else if (MPFR_UNLIKELY (d == ((__float128) -1.0 / (__float128) 0.0)))
+  else if (MPFR_UNLIKELY (d < -MPFR_FLOAT128_MAX))
     {
-      mpfr_set_inf (r, -1);
+      MPFR_SET_INF (r);
+      MPFR_SET_NEG (r);
       return 0;
     }
   /* Check for ZERO */
diff --git a/tests/tset_float128.c b/tests/tset_float128.c
index ad50bf820..a325ceecc 100644
--- a/tests/tset_float128.c
+++ b/tests/tset_float128.c
@@ -40,10 +40,11 @@ check_special (void)
 
   mpfr_init2 (x, 113);
 
+#if !defined(MPFR_ERRDIVZERO)
   /* check NaN */
   f = 0.0 / 0.0;
   mpfr_set_float128 (x, f, MPFR_RNDN);
-  if (mpfr_nan_p (x) == 0)
+  if (! mpfr_nan_p (x))
     {
       printf ("Error in mpfr_set_float128(x, NaN)\n");
       exit (1);
@@ -59,7 +60,7 @@ check_special (void)
   /* check +Inf */
   f = 1.0 / 0.0;
   mpfr_set_float128 (x, f, MPFR_RNDN);
-  if (mpfr_inf_p (x) == 0 || mpfr_sgn (x) < 0)
+  if (! mpfr_inf_p (x) || MPFR_IS_NEG (x))
     {
       printf ("Error in mpfr_set_float128(x, +Inf)\n");
       exit (1);
@@ -74,7 +75,7 @@ check_special (void)
   /* check -Inf */
   f = -1.0 / 0.0;
   mpfr_set_float128 (x, f, MPFR_RNDN);
-  if (mpfr_inf_p (x) == 0 || mpfr_sgn (x) > 0)
+  if (! mpfr_inf_p (x) || MPFR_IS_POS (x))
     {
       printf ("Error in mpfr_set_float128(x, -Inf)\n");
       exit (1);
@@ -85,36 +86,58 @@ check_special (void)
       printf ("Error in mpfr_get_float128(-Inf)\n");
       exit (1);
     }
+#endif
 
   /* check +0 */
   f = 0.0;
   mpfr_set_float128 (x, f, MPFR_RNDN);
-  if (mpfr_zero_p (x) == 0 || mpfr_sgn (x) < 0)
+  if (! mpfr_zero_p (x) || MPFR_IS_NEG (x))
     {
       printf ("Error in mpfr_set_float128(x, +0)\n");
       exit (1);
     }
   f = mpfr_get_float128 (x, MPFR_RNDN);
-  if (f != 0.0 || 1 / f != 1 / 0.0)
+  if (f != 0.0)  /* the sign is not checked */
+    {
+      printf ("Error in mpfr_get_float128(+0.0)\n");
+      exit (1);
+    }
+#if !defined(MPFR_ERRDIVZERO) && defined(HAVE_SIGNEDZ)
+  if (1 / f != 1 / 0.0)  /* check the sign */
     {
       printf ("Error in mpfr_get_float128(+0.0)\n");
       exit (1);
     }
+#endif
 
   /* check -0 */
   f = -0.0;
   mpfr_set_float128 (x, f, MPFR_RNDN);
-  if (mpfr_zero_p (x) == 0 || mpfr_sgn (x) > 0)
+  if (! mpfr_zero_p (x))
+    {
+      printf ("Error in mpfr_set_float128(x, -0)\n");
+      exit (1);
+    }
+#if defined(HAVE_SIGNEDZ)
+  if (MPFR_IS_POS (x))
     {
       printf ("Error in mpfr_set_float128(x, -0)\n");
       exit (1);
     }
+#endif
   f = mpfr_get_float128 (x, MPFR_RNDN);
-  if (f != -0.0 || 1 / f != 1 / -0.0)
+  if (f != -0.0)  /* the sign is not checked */
+    {
+      printf ("Error in mpfr_get_float128(-0.0)\n");
+      exit (1);
+    }
+#if !defined(MPFR_ERRDIVZERO) && defined(HAVE_SIGNEDZ)
+  if (1 / f != 1 / -0.0)  /* check the sign */
     {
       printf ("Error in mpfr_get_float128(-0.0)\n");
       exit (1);
     }
+#endif
 
   mpfr_clear (x);
 }