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author | daney <daney@280ebfd0-de03-0410-8827-d642c229c3f4> | 2001-11-08 16:21:56 +0000 |
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committer | daney <daney@280ebfd0-de03-0410-8827-d642c229c3f4> | 2001-11-08 16:21:56 +0000 |
commit | 110ae3b2737f061c35f05eafbda0dd88f06c0bc0 (patch) | |
tree | c5f9d2138df03ed9477ab412a676deb47e1f71ac /pow_si.c | |
parent | 4aa73d6157d7fa6e33cbbd5a77bec93bc85b2ed5 (diff) | |
download | mpfr-110ae3b2737f061c35f05eafbda0dd88f06c0bc0.tar.gz |
exporte pow_si from pow2.c to pow_si.c
git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1474 280ebfd0-de03-0410-8827-d642c229c3f4
Diffstat (limited to 'pow_si.c')
-rw-r--r-- | pow_si.c | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/pow_si.c b/pow_si.c new file mode 100644 index 000000000..6f9993307 --- /dev/null +++ b/pow_si.c @@ -0,0 +1,172 @@ +/* mpfr_pow_si -- power function x^y with y an unsigned int + +Copyright (C) 2001 Free Software Foundation. + +This file is part of the MPFR Library. + +The MPFR Library is free software; you can redistribute it and/or modify +it under the terms of the GNU Library General Public License as published by +the Free Software Foundation; either version 2 of the License, or (at your +option) any later version. + +The 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 Library General Public +License for more details. + +You should have received a copy of the GNU Library General Public License +along with the MPFR Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include <stdio.h> +#include <math.h> +#include "gmp.h" +#include "gmp-impl.h" +#include "mpfr.h" +#include "mpfr-impl.h" + + /* The computation of y=pow(x,z) is done by + + y=pow_ui(x,z) if z>0 + else + y=1/pow_ui(x,z) if z<0 + */ + +int mpfr_pow_si _PROTO ((mpfr_ptr, mpfr_srcptr, long int, mp_rnd_t)); + +int +#if __STDC__ +mpfr_pow_si (mpfr_ptr y, mpfr_srcptr x, long int n, mp_rnd_t rnd_mode) +#else +mpfr_pow_si (y, x, n, rnd) + mpfr_ptr y; + mpfr_srcptr x; + long int n; + mp_rnd_t rnd_mode; +#endif +{ + + if (n>0) + return mpfr_pow_ui(y,x,(unsigned long int)n,rnd_mode); + else + { + + int inexact = 0; + + n=-n; + + /* x is NaN*/ + if (MPFR_IS_NAN(x)) + { + MPFR_SET_NAN(y); + return 1; + } + MPFR_CLEAR_NAN(y); + + /* n=0 */ + if(n==0) + return mpfr_set_ui(y,1,GMP_RNDN);; + + /* case x is INF */ + if(MPFR_IS_INF(x)) + { + if(MPFR_SIGN(x)>0) /* +Inf */ + { + MPFR_SET_ZERO(y); + if(MPFR_SIGN(y) < 0) + MPFR_CHANGE_SIGN(y); + return 0; + } + else + { + MPFR_SET_ZERO(y); /* -Inf */ + if(!(n%2)) /* n is odd */ + { + if(MPFR_SIGN(y) > 0) + MPFR_CHANGE_SIGN(y); + } + else /* n is not odd */ + { + if(MPFR_SIGN(y) < 0) + MPFR_CHANGE_SIGN(y); + } + return 0; + } + } + + /* case x=0 */ + if(mpfr_cmp_ui(x,0) == 0) + { + if(!(n%2)) /* n is odd */ + { + MPFR_SET_INF(y); + MPFR_SET_SAME_SIGN(y,x); + DIVIDE_BY_ZERO; /* Execption GMP*/ + return 0; + } + else /* n is not odd */ + { + MPFR_SET_INF(y); + if(MPFR_SIGN(y) < 0) + MPFR_CHANGE_SIGN(y); + DIVIDE_BY_ZERO; /* Execption GMP*/ + return 0; + } + } + + MPFR_CLEAR_INF(y); + + /* General case */ + { + /* Declaration of the intermediary variable */ + mpfr_t t, ti; + + /* Declaration of the size variable */ + mp_prec_t Nx = MPFR_PREC(x); /* Precision of input variable */ + mp_prec_t Ny = MPFR_PREC(y); /* Precision of input variable */ + + mp_prec_t Nt; /* Precision of the intermediary variable */ + long int err; /* Precision of error */ + + /* compute the precision of intermediary variable */ + Nt=MAX(Nx,Ny); + /* the optimal number of bits : see algorithms.ps */ + Nt=Nt+3+_mpfr_ceil_log2(Nt); + + /* initialise of intermediary variable */ + mpfr_init(t); + mpfr_init(ti); + + do { + + /* reactualisation of the precision */ + mpfr_set_prec(t,Nt); + mpfr_set_prec(ti,Nt); + + /* compute 1/(x^n) n>0*/ + mpfr_pow_ui(ti,y,(unsigned long int)(n),GMP_RNDN); + mpfr_ui_div(t,1,ti,GMP_RNDN); + + /* estimation of the error -- see pow function in algorithms.ps*/ + err = Nt - 3; + + /* actualisation of the precision */ + Nt += 10; + + } while (err<0 || !mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny)); + + inexact = mpfr_set(y,t,rnd_mode); + mpfr_clear(t); + mpfr_clear(ti); + } + return inexact; + } +} + + + + + + + |