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Annotation of OpenXM_contrib/gmp/mpfr/cosh.c, Revision 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: }