Annotation of OpenXM_contrib/gmp/mpfr/expm1.c, Revision 1.1
1.1 ! ohara 1: /* mpfr_expm1 -- Compute exp(x)-1
! 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 "gmp.h"
! 23: #include "gmp-impl.h"
! 24: #include "mpfr.h"
! 25: #include "mpfr-impl.h"
! 26:
! 27: /* The computation of expm1 is done by
! 28:
! 29: expm1(x)=exp(x)-1
! 30: */
! 31:
! 32: int
! 33: mpfr_expm1 (mpfr_ptr y, mpfr_srcptr x , mp_rnd_t rnd_mode)
! 34: {
! 35: int inexact = 0;
! 36:
! 37: if (MPFR_IS_NAN(x))
! 38: {
! 39: MPFR_SET_NAN(y);
! 40: MPFR_RET_NAN;
! 41: }
! 42:
! 43: MPFR_CLEAR_NAN(y);
! 44:
! 45: /* check for inf or -inf (expm1(-inf)=-1) */
! 46: if (MPFR_IS_INF(x))
! 47: {
! 48: if (MPFR_SIGN(x) > 0)
! 49: {
! 50: MPFR_SET_INF(y);
! 51: MPFR_SET_POS(y);
! 52: return 0;
! 53: }
! 54: else
! 55: return mpfr_set_si(y, -1, rnd_mode);
! 56: }
! 57:
! 58: MPFR_CLEAR_INF(y);
! 59:
! 60: if(MPFR_IS_ZERO(x))
! 61: {
! 62: MPFR_SET_ZERO(y); /* expm1(+/- 0) = +/- 0 */
! 63: MPFR_SET_SAME_SIGN(y,x);
! 64: MPFR_RET(0);
! 65: }
! 66:
! 67: /* General case */
! 68: {
! 69: /* Declaration of the intermediary variable */
! 70: mpfr_t te,t;
! 71:
! 72: /* Declaration of the size variable */
! 73: mp_prec_t Nx = MPFR_PREC(x); /* Precision of input variable */
! 74: mp_prec_t Ny = MPFR_PREC(y); /* Precision of input variable */
! 75:
! 76: mp_prec_t Nt; /* Precision of the intermediary variable */
! 77: long int err; /* Precision of error */
! 78:
! 79: /* compute the precision of intermediary variable */
! 80: Nt=MAX(Nx,Ny);
! 81: /* the optimal number of bits : see algorithms.ps */
! 82: Nt=Nt+5+_mpfr_ceil_log2(Nt);
! 83:
! 84: /* initialise of intermediary variable */
! 85: mpfr_init(t);
! 86: mpfr_init(te);
! 87:
! 88: /* First computation of cosh */
! 89: do {
! 90:
! 91: /* reactualisation of the precision */
! 92: mpfr_set_prec(t,Nt);
! 93: mpfr_set_prec(te,Nt);
! 94:
! 95: /* compute expm1 */
! 96: mpfr_exp(te,x,GMP_RNDN); /* exp(x)*/
! 97: mpfr_sub_ui(t,te,1,GMP_RNDN); /* exp(x)-1 */
! 98:
! 99: /* estimation of the error */
! 100: /*err=Nt-(_mpfr_ceil_log2(1+pow(2,MPFR_EXP(te)-MPFR_EXP(t))));*/
! 101: err=Nt-(MAX(MPFR_EXP(te)-MPFR_EXP(t),0)+1);
! 102:
! 103: /* actualisation of the precision */
! 104: Nt += 10;
! 105:
! 106: } while ((err <0) || !mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny));
! 107:
! 108: inexact = mpfr_set(y,t,rnd_mode);
! 109:
! 110: mpfr_clear(t);
! 111: mpfr_clear(te);
! 112: }
! 113: return inexact;
! 114: }
FreeBSD-CVSweb <freebsd-cvsweb@FreeBSD.org>