New function mpfr_min_prec.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@6102 280ebfd0-de03-0410-8827-d642c229c3f4

2 files changed, 66 insertions, 1 deletions

diff --git a/Makefile.am b/Makefile.am
index 4bf75a294..07fc65008 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -8,7 +8,7 @@ include_HEADERS = mpfr.h mpf2mpfr.h
 
 lib_LTLIBRARIES = libmpfr.la
 
-libmpfr_la_SOURCES = mpfr.h mpf2mpfr.h mpfr-gmp.h mpfr-impl.h mpfr-longlong.h mpfr-thread.h exceptions.c extract.c uceil_exp2.c uceil_log2.c ufloor_log2.c add.c add1.c add_ui.c agm.c clear.c cmp.c cmp_abs.c cmp_si.c cmp_ui.c comparisons.c div_2exp.c div_2si.c div_2ui.c div.c div_ui.c dump.c eq.c exp10.c exp2.c exp3.c exp.c frac.c get_d.c get_exp.c get_str.c init.c inp_str.c isinteger.c isinf.c isnan.c isnum.c const_log2.c log.c modf.c mul_2exp.c mul_2si.c mul_2ui.c mul.c mul_ui.c neg.c next.c out_str.c printf.c vasprintf.c const_pi.c pow.c pow_si.c pow_ui.c print_raw.c print_rnd_mode.c random2.c reldiff.c round_prec.c set.c setmax.c setmin.c set_d.c set_dfl_prec.c set_exp.c set_rnd.c set_f.c set_prc_raw.c set_prec.c set_q.c set_si.c set_str.c set_str_raw.c set_ui.c set_z.c sqrt.c sqrt_ui.c sub.c sub1.c sub_ui.c rint.c ui_div.c ui_sub.c urandomb.c get_z_exp.c swap.c  factorial.c cosh.c sinh.c tanh.c sinh_cosh.c acosh.c asinh.c atanh.c atan.c cmp2.c exp_2.c asin.c const_euler.c cos.c sin.c tan.c fma.c fms.c hypot.c log1p.c expm1.c log2.c log10.c ui_pow.c ui_pow_ui.c minmax.c dim.c signbit.c copysign.c setsign.c gmp_op.c init2.c acos.c sin_cos.c set_nan.c set_inf.c powerof2.c gamma.c set_ld.c get_ld.c cbrt.c volatile.c fits_s.h fits_sshort.c fits_sint.c fits_slong.c fits_u.h fits_ushort.c fits_uint.c fits_ulong.c fits_uintmax.c fits_intmax.c get_si.c get_ui.c zeta.c cmp_d.c erf.c inits.c inits2.c clears.c sgn.c check.c sub1sp.c version.c mpn_exp.c mpfr-gmp.c mp_clz_tab.c sum.c add1sp.c free_cache.c si_op.c cmp_ld.c set_ui_2exp.c set_si_2exp.c set_uj.c set_sj.c get_sj.c get_uj.c get_z.c iszero.c cache.c sqr.c int_ceil_log2.c isqrt.c strtofr.c pow_z.c logging.c mulders.c get_f.c round_p.c erfc.c atan2.c subnormal.c const_catalan.c root.c gen_inverse.h sec.c csc.c cot.c eint.c sech.c csch.c coth.c round_near_x.c constant.c abort_prec_max.c stack_interface.c lngamma.c zeta_ui.c set_d64.c get_d64.c jn.c yn.c rem1.c get_patches.c add_d.c sub_d.c d_sub.c mul_d.c div_d.c d_div.c li2.c rec_sqrt.c
+libmpfr_la_SOURCES = mpfr.h mpf2mpfr.h mpfr-gmp.h mpfr-impl.h mpfr-longlong.h mpfr-thread.h exceptions.c extract.c uceil_exp2.c uceil_log2.c ufloor_log2.c add.c add1.c add_ui.c agm.c clear.c cmp.c cmp_abs.c cmp_si.c cmp_ui.c comparisons.c div_2exp.c div_2si.c div_2ui.c div.c div_ui.c dump.c eq.c exp10.c exp2.c exp3.c exp.c frac.c get_d.c get_exp.c get_str.c init.c inp_str.c isinteger.c isinf.c isnan.c isnum.c const_log2.c log.c modf.c mul_2exp.c mul_2si.c mul_2ui.c mul.c mul_ui.c neg.c next.c out_str.c printf.c vasprintf.c const_pi.c pow.c pow_si.c pow_ui.c print_raw.c print_rnd_mode.c random2.c reldiff.c round_prec.c set.c setmax.c setmin.c set_d.c set_dfl_prec.c set_exp.c set_rnd.c set_f.c set_prc_raw.c set_prec.c set_q.c set_si.c set_str.c set_str_raw.c set_ui.c set_z.c sqrt.c sqrt_ui.c sub.c sub1.c sub_ui.c rint.c ui_div.c ui_sub.c urandomb.c get_z_exp.c swap.c  factorial.c cosh.c sinh.c tanh.c sinh_cosh.c acosh.c asinh.c atanh.c atan.c cmp2.c exp_2.c asin.c const_euler.c cos.c sin.c tan.c fma.c fms.c hypot.c log1p.c expm1.c log2.c log10.c ui_pow.c ui_pow_ui.c minmax.c dim.c signbit.c copysign.c setsign.c gmp_op.c init2.c acos.c sin_cos.c set_nan.c set_inf.c powerof2.c gamma.c set_ld.c get_ld.c cbrt.c volatile.c fits_s.h fits_sshort.c fits_sint.c fits_slong.c fits_u.h fits_ushort.c fits_uint.c fits_ulong.c fits_uintmax.c fits_intmax.c get_si.c get_ui.c zeta.c cmp_d.c erf.c inits.c inits2.c clears.c sgn.c check.c sub1sp.c version.c mpn_exp.c mpfr-gmp.c mp_clz_tab.c sum.c add1sp.c free_cache.c si_op.c cmp_ld.c set_ui_2exp.c set_si_2exp.c set_uj.c set_sj.c get_sj.c get_uj.c get_z.c iszero.c cache.c sqr.c int_ceil_log2.c isqrt.c strtofr.c pow_z.c logging.c mulders.c get_f.c round_p.c erfc.c atan2.c subnormal.c const_catalan.c root.c gen_inverse.h sec.c csc.c cot.c eint.c sech.c csch.c coth.c round_near_x.c constant.c abort_prec_max.c stack_interface.c lngamma.c zeta_ui.c set_d64.c get_d64.c jn.c yn.c rem1.c get_patches.c add_d.c sub_d.c d_sub.c mul_d.c div_d.c d_div.c li2.c rec_sqrt.c min_prec.c
 
 libmpfr_la_LIBADD = @LIBOBJS@
 
diff --git a/min_prec.c b/min_prec.c
new file mode 100644
index 000000000..db0ae25c7
--- /dev/null
+++ b/min_prec.c
@@ -0,0 +1,65 @@
+/* mpfr_min_prec -- minimal size in bits to hold the mantissa
+
+Copyright 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 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.LIB.  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. */
+
+#include "mpfr-impl.h"
+
+int
+mpfr_min_prec (mpfr_srcptr x)
+{
+  mp_limb_t *mx;
+  mp_prec_t px;
+  mp_size_t n;
+  int res, i;
+
+
+  if (MPFR_IS_NAN (x) || MPFR_IS_INF (x))
+    return 0;
+
+  if (MPFR_IS_ZERO (x))
+    return 0;
+
+  mx = MPFR_MANT (x);
+  px = MPFR_PREC (x);
+
+  res = 0;
+  /* Count full limbs set to zero */
+  for (n = (px - 1) / BITS_PER_MP_LIMB; mx[n] == 0; n--)
+    {
+      res += BITS_PER_MP_LIMB;
+    }
+
+  i = 0;
+  /* mx[n] is now the first limb which is not null. Count number
+   * of null bits in mx[n], from the right */
+  while ((i < BITS_PER_MP_LIMB) && (mx[n] & (1 << i) == 0))
+    i++;
+
+  res += i;
+  /* If we have trailing zero bits because the precision
+   * is not a multiple of BITS_PER_MP_LIMB, we must not count
+   * those. */
+  i = px % BITS_PER_MP_LIMB;
+  if (px != 0)
+    res -= BITS_PER_MP_LIMB - i;
+
+  return px - res;
+}