Imported gcc-4.4.3

[msp430-gcc.git] / mpfr / log10.c

diff --git a/mpfr/log10.c b/mpfr/log10.c
new file mode 100644 (file)
index 0000000..10e304d
--- /dev/null
+++ b/mpfr/log10.c
@@ -0,0 +1,144 @@
+/* mpfr_log10 -- logarithm in base 10.
+
+Copyright 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
+Contributed by the Arenaire and Cacao projects, INRIA.
+
+This file is part of the GNU MPFR Library.
+
+The GNU MPFR Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or (at your
+option) any later version.
+
+The GNU MPFR Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MPFR Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
+MA 02110-1301, USA. */
+
+#define MPFR_NEED_LONGLONG_H
+#include "mpfr-impl.h"
+
+ /* The computation of r=log10(a)
+
+    r=log10(a)=log(a)/log(10)
+ */
+
+int
+mpfr_log10 (mpfr_ptr r, mpfr_srcptr a, mp_rnd_t rnd_mode)
+{
+  int inexact;
+  MPFR_SAVE_EXPO_DECL (expo);
+
+  /* If a is NaN, the result is NaN */
+  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (a)))
+    {
+      if (MPFR_IS_NAN (a))
+        {
+          MPFR_SET_NAN (r);
+          MPFR_RET_NAN;
+        }
+      /* check for infinity before zero */
+      else if (MPFR_IS_INF (a))
+        {
+          if (MPFR_IS_NEG (a))
+            /* log10(-Inf) = NaN */
+            {
+              MPFR_SET_NAN (r);
+              MPFR_RET_NAN;
+            }
+          else /* log10(+Inf) = +Inf */
+            {
+              MPFR_SET_INF (r);
+              MPFR_SET_POS (r);
+              MPFR_RET (0); /* exact */
+            }
+        }
+      else /* a = 0 */
+        {
+          MPFR_ASSERTD (MPFR_IS_ZERO (a));
+          MPFR_SET_INF (r);
+          MPFR_SET_NEG (r);
+          MPFR_RET (0); /* log10(0) is an exact -infinity */
+        }
+    }
+
+  /* If a is negative, the result is NaN */
+  if (MPFR_UNLIKELY (MPFR_IS_NEG (a)))
+    {
+      MPFR_SET_NAN (r);
+      MPFR_RET_NAN;
+    }
+
+  /* If a is 1, the result is 0 */
+  if (mpfr_cmp_ui (a, 1) == 0)
+    {
+      MPFR_SET_ZERO (r);
+      MPFR_SET_POS (r);
+      MPFR_RET (0); /* result is exact */
+    }
+
+  MPFR_SAVE_EXPO_MARK (expo);
+
+  /* General case */
+  {
+    /* Declaration of the intermediary variable */
+    mpfr_t t, tt;
+    MPFR_ZIV_DECL (loop);
+    /* Declaration of the size variable */
+    mp_prec_t Ny = MPFR_PREC(r);   /* Precision of output variable */
+    mp_prec_t Nt;        /* Precision of the intermediary variable */
+    mp_exp_t  err;                           /* Precision of error */
+
+    /* compute the precision of intermediary variable */
+    /* the optimal number of bits : see algorithms.tex */
+    Nt = Ny + 4 + MPFR_INT_CEIL_LOG2 (Ny);
+
+    /* initialise of intermediary variables */
+    mpfr_init2 (t, Nt);
+    mpfr_init2 (tt, Nt);
+
+    /* First computation of log10 */
+    MPFR_ZIV_INIT (loop, Nt);
+    for (;;)
+      {
+        /* compute log10 */
+        mpfr_set_ui (t, 10, GMP_RNDN);   /* 10 */
+        mpfr_log (t, t, GMP_RNDD);       /* log(10) */
+        mpfr_log (tt, a, GMP_RNDN);      /* log(a) */
+        mpfr_div (t, tt, t, GMP_RNDN);   /* log(a)/log(10) */
+
+        /* estimation of the error */
+        err = Nt - 4;
+        if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
+          break;
+
+        /* log10(10^n) is exact:
+           FIXME: Can we have 10^n exactly representable as a mpfr_t
+           but n can't fit an unsigned long? */
+        if (MPFR_IS_POS (t)
+            && mpfr_integer_p (t) && mpfr_fits_ulong_p (t, GMP_RNDN)
+            && !mpfr_ui_pow_ui (tt, 10, mpfr_get_ui (t, GMP_RNDN), GMP_RNDN)
+            && mpfr_cmp (a, tt) == 0)
+          break;
+
+        /* actualisation of the precision */
+        MPFR_ZIV_NEXT (loop, Nt);
+        mpfr_set_prec (t, Nt);
+        mpfr_set_prec (tt, Nt);
+      }
+    MPFR_ZIV_FREE (loop);
+
+    inexact = mpfr_set (r, t, rnd_mode);
+
+    mpfr_clear (t);
+    mpfr_clear (tt);
+  }
+
+  MPFR_SAVE_EXPO_FREE (expo);
+  return mpfr_check_range (r, inexact, rnd_mode);
+}