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author | daney <daney@280ebfd0-de03-0410-8827-d642c229c3f4> | 2001-04-05 17:14:44 +0000 |
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committer | daney <daney@280ebfd0-de03-0410-8827-d642c229c3f4> | 2001-04-05 17:14:44 +0000 |
commit | 9f215fb99185b459794d2e3999d652ebc5a9d812 (patch) | |
tree | 3d6d7a9beb9cf7e49ec654b9d43abe06737897f2 /tanh.c | |
parent | 8b84f420b10d26361d003dcd3c9588635ff7314b (diff) | |
download | mpfr-9f215fb99185b459794d2e3999d652ebc5a9d812.tar.gz |
new file function
git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1057 280ebfd0-de03-0410-8827-d642c229c3f4
Diffstat (limited to 'tanh.c')
-rw-r--r-- | tanh.c | 140 |
1 files changed, 140 insertions, 0 deletions
@@ -0,0 +1,140 @@ +/* mpfr_tanh -- Hyperbolic Tangent of Unsigned Integer Number + +Copyright (C) 1999 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 "gmp.h" +#include "gmp-impl.h" +#include "mpfr.h" +#include "mpfr-impl.h" + + /* The computation of cosh is done by + + tanh= [e^(x)^2-1]/+[e^(x)^2+1] + */ +int mpfr_tanh _PROTO((mpfr_ptr, mpfr_srcptr, mp_rnd_t)); + +int +#if __STDC__ +mpfr_tanh (mpfr_ptr y, mpfr_srcptr x , mp_rnd_t rnd_mode) +#else +mpfr_tanh (y, x, rnd_mode) + mpfr_ptr y; + mpfr_srcptr x; + mp_rnd_t rnd_mode; +#endif +{ + + /****** Declaration ******/ + + /* Variable of Intermediary Calculation*/ + mpfr_t t; + + /* Variable of Intermediary Calculation*/ + mpfr_t te,ta,tb; + + int round; + int boucle; + + mp_prec_t Nx; /* Precision of input variable */ + mp_prec_t Ny; /* Precision of output variable */ + mp_prec_t Nt; /* Precision of Intermediary Calculation variable */ + mp_prec_t err; /* Precision of error */ + + + if (MPFR_IS_NAN(x)) { MPFR_SET_NAN(y); return 1; } + MPFR_CLEAR_NAN(y); + + if (MPFR_IS_INF(x)){ + + if(MPFR_SIGN(x) > 0) + mpfr_set_si(y,1,GMP_RNDN); /* tanh(inf) = 1 */ + else + mpfr_set_si(y,-1,GMP_RNDN); /* tanh(inf) = -1 */ + + return(0); + } + + if(!MPFR_NOTZERO(x)){ /* tanh(0) = 0 */ + MPFR_CLEAR_INF(y); + MPFR_SET_ZERO(y); + if (MPFR_SIGN(y) < 0) MPFR_CHANGE_SIGN(y); + return(0); + } + else{ + + + /* Initialisation of the Precision */ + Nx=MPFR_PREC(x); + Ny=MPFR_PREC(y); + + /* compute the size of intermediary variable */ + if(Ny>=Nx) + Nt=Ny+2*(BITS_PER_CHAR); + else + Nt=Nx+2*(BITS_PER_CHAR); + + boucle=1; + + /* initialise of intermediary variable */ + mpfr_init2(t,Nt); + mpfr_init2(te,Nt); + mpfr_init2(ta,Nt); + mpfr_init2(tb,Nt); + + while(boucle==1){ + + + /* compute tanh */ + mpfr_mul_2exp(te,x,1,GMP_RNDN); /* 2x */ + mpfr_exp(te,te,GMP_RNDN); /* exp(2x) */ + mpfr_add_ui(ta,te,1,GMP_RNDN); /* exp(2x) + 1*/ + mpfr_sub_ui(tb,te,1,GMP_RNDN); /* exp(2x) - 1*/ + mpfr_div(t,tb,ta,GMP_RNDN); /* (exp(2x)-1)/(exp(2x)+1)*/ + + err=Nt-1-((MPFR_EXP(te)-MPFR_EXP(tb))); + + round=mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny); + + if(round == 1){ + mpfr_set(y,t,rnd_mode); + boucle=0; + } + else{ + Nt=Nt+10; + /* re-initialise of intermediary variable */ + mpfr_set_prec(t,Nt); + mpfr_set_prec(te,Nt); + mpfr_set_prec(ta,Nt); + mpfr_set_prec(tb,Nt); + boucle=1; + } + + } + + mpfr_clear(t); + mpfr_clear(te); + mpfr_clear(ta); + mpfr_clear(tb); + return(1); + + + } +} |