summaryrefslogtreecommitdiff
path: root/Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c
diff options
context:
space:
mode:
Diffstat (limited to 'Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c')
-rw-r--r--Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c142
1 files changed, 142 insertions, 0 deletions
diff --git a/Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c b/Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c
new file mode 100644
index 00000000000..d95497bfeac
--- /dev/null
+++ b/Build/source/libs/mpfr/mpfr-3.1.2/src/log2.c
@@ -0,0 +1,142 @@
+/* mpfr_log2 -- log base 2
+
+Copyright 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
+Contributed by the AriC and Caramel 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 3 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.LESSER. If not, see
+http://www.gnu.org/licenses/ or 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=log2(a)
+ r=log2(a)=log(a)/log(2) */
+
+int
+mpfr_log2 (mpfr_ptr r, mpfr_srcptr a, mpfr_rnd_t rnd_mode)
+{
+ int inexact;
+ MPFR_SAVE_EXPO_DECL (expo);
+
+ MPFR_LOG_FUNC
+ (("a[%Pu]=%.*Rg rnd=%d", mpfr_get_prec (a), mpfr_log_prec, a, rnd_mode),
+ ("r[%Pu]=%.*Rg inexact=%d", mpfr_get_prec (r), mpfr_log_prec, r,
+ inexact));
+
+ if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (a)))
+ {
+ /* If a is NaN, the result is NaN */
+ 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))
+ /* log(-Inf) = NaN */
+ {
+ MPFR_SET_NAN (r);
+ MPFR_RET_NAN;
+ }
+ else /* log(+Inf) = +Inf */
+ {
+ MPFR_SET_INF (r);
+ MPFR_SET_POS (r);
+ MPFR_RET (0);
+ }
+ }
+ else /* a is zero */
+ {
+ MPFR_ASSERTD (MPFR_IS_ZERO (a));
+ MPFR_SET_INF (r);
+ MPFR_SET_NEG (r);
+ mpfr_set_divby0 ();
+ MPFR_RET (0); /* log2(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_UNLIKELY (mpfr_cmp_ui (a, 1) == 0))
+ {
+ MPFR_SET_ZERO (r);
+ MPFR_SET_POS (r);
+ MPFR_RET (0); /* only "normal" case where the result is exact */
+ }
+
+ /* If a is 2^N, log2(a) is exact*/
+ if (MPFR_UNLIKELY (mpfr_cmp_ui_2exp (a, 1, MPFR_GET_EXP (a) - 1) == 0))
+ return mpfr_set_si(r, MPFR_GET_EXP (a) - 1, rnd_mode);
+
+ MPFR_SAVE_EXPO_MARK (expo);
+
+ /* General case */
+ {
+ /* Declaration of the intermediary variable */
+ mpfr_t t, tt;
+ /* Declaration of the size variable */
+ mpfr_prec_t Ny = MPFR_PREC(r); /* target precision */
+ mpfr_prec_t Nt; /* working precision */
+ mpfr_exp_t err; /* error */
+ MPFR_ZIV_DECL (loop);
+
+ /* compute the precision of intermediary variable */
+ /* the optimal number of bits : see algorithms.tex */
+ Nt = Ny + 3 + MPFR_INT_CEIL_LOG2 (Ny);
+
+ /* initialise of intermediary variable */
+ mpfr_init2 (t, Nt);
+ mpfr_init2 (tt, Nt);
+
+ /* First computation of log2 */
+ MPFR_ZIV_INIT (loop, Nt);
+ for (;;)
+ {
+ /* compute log2 */
+ mpfr_const_log2(t,MPFR_RNDD); /* log(2) */
+ mpfr_log(tt,a,MPFR_RNDN); /* log(a) */
+ mpfr_div(t,tt,t,MPFR_RNDN); /* log(a)/log(2) */
+
+ /* estimation of the error */
+ err = Nt-3;
+ if (MPFR_LIKELY (MPFR_CAN_ROUND (t, err, Ny, rnd_mode)))
+ 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);
+}