Return to cosh.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpfr

Annotation of OpenXM_contrib/gmp/mpfr/cosh.c, Revision 1.1.1.1

1.1       ohara       1: /* mpfr_cosh -- hyperbolic cosine
                      2:
                      3: Copyright 2001, 2002 Free Software Foundation.
                      4:
                      5: This file is part of the MPFR Library.
                      6:
                      7: The MPFR Library is free software; you can redistribute it and/or modify
                      8: it under the terms of the GNU Lesser General Public License as published by
                      9: the Free Software Foundation; either version 2.1 of the License, or (at your
                     10: option) any later version.
                     11:
                     12: The MPFR Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Lesser General Public License
                     18: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
                     20: MA 02111-1307, USA. */
                     21:
                     22: #include <stdio.h>
                     23: #include "gmp.h"
                     24: #include "gmp-impl.h"
                     25: #include "mpfr.h"
                     26: #include "mpfr-impl.h"
                     27:
                     28:  /* The computation of cosh is done by
                     29:
                     30:     cosh= 1/2[e^(x)+e^(-x)]
                     31:  */
                     32:
                     33: int
                     34: mpfr_cosh (mpfr_ptr y, mpfr_srcptr xt , mp_rnd_t rnd_mode)
                     35: {
                     36:
                     37:   /****** Declaration ******/
                     38:     mpfr_t x;
                     39:     mp_prec_t Nxt = MPFR_PREC(xt);
                     40:     int inexact =0;
                     41:
                     42:     if (MPFR_IS_NAN(xt))
                     43:       {
                     44:         MPFR_SET_NAN(y);
                     45:         MPFR_RET_NAN;
                     46:       }
                     47:     MPFR_CLEAR_NAN(y);
                     48:
                     49:     if (MPFR_IS_INF(xt))
                     50:       {
                     51:         MPFR_SET_INF(y);
                     52:         if (MPFR_SIGN(y) < 0)
                     53:           MPFR_CHANGE_SIGN(y);
                     54:         MPFR_RET(0);
                     55:       }
                     56:
                     57:     MPFR_CLEAR_INF(y);
                     58:
                     59:     if (MPFR_IS_ZERO(xt))
                     60:       return mpfr_set_ui(y,1,rnd_mode); /* cosh(0) = 1 */
                     61:
                     62:     mpfr_init2(x,Nxt);
                     63:     mpfr_set4(x, xt, GMP_RNDN, 1);
                     64:
                     65:     /* General case */
                     66:     {
                     67:     /* Declaration of the intermediary variable */
                     68:       mpfr_t t, te,ti;
                     69:
                     70:       /* Declaration of the size variable */
                     71:       mp_prec_t Nx = Nxt;   /* Precision of input variable */
                     72:       mp_prec_t Ny = MPFR_PREC(y);   /* Precision of input variable */
                     73:
                     74:       mp_prec_t Nt;   /* Precision of the intermediary variable */
                     75:       long int err;  /* Precision of error */
                     76:
                     77:       /* compute the precision of intermediary variable */
                     78:       Nt=MAX(Nx,Ny);
                     79:       /* the optimal number of bits : see algorithms.ps */
                     80:       Nt=Nt+3+_mpfr_ceil_log2(Nt);
                     81:
                     82:
                     83:       /* initialise of intermediary    variable */
                     84:       mpfr_init(t);
                     85:       mpfr_init(te);
                     86:       mpfr_init(ti);
                     87:
                     88:
                     89:       /* First computation of cosh */
                     90:       do {
                     91:
                     92:        /* reactualisation of the precision */
                     93:
                     94:        mpfr_set_prec(t,Nt);
                     95:        mpfr_set_prec(te,Nt);
                     96:        mpfr_set_prec(ti,Nt);
                     97:
                     98:        /* compute cosh */
                     99:        mpfr_exp(te,x,GMP_RNDD);         /* exp(x) */
                    100:        mpfr_ui_div(ti,1,te,GMP_RNDU);   /* 1/exp(x) */
                    101:        mpfr_add(t,te,ti,GMP_RNDN);      /* exp(x) + 1/exp(x)*/
                    102:        mpfr_div_2ui(t,t,1,GMP_RNDN);    /* 1/2(exp(x) + 1/exp(x))*/
                    103:
                    104:        /* estimation of the error */
                    105:        err=Nt-3;
                    106:
                    107:        /* actualisation of the precision */
                    108:        Nt += 10;
                    109:
                    110:       } while ((err <0) || !mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny));
                    111:
                    112:       inexact = mpfr_set(y,t,rnd_mode);
                    113:
                    114:       mpfr_clear(t);
                    115:       mpfr_clear(ti);
                    116:       mpfr_clear(te);
                    117:     }
                    118:     mpfr_clear(x);
                    119:     return inexact;
                    120:
                    121: }