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Annotation of OpenXM_contrib/gmp/mpfr/pow_si.c, Revision 1.1

1.1     ! ohara       1: /* mpfr_pow_si -- power function x^y with y an unsigned int
        !             2:
        !             3: Copyright 2001, 2002 Free Software Foundation, Inc.
        !             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 y=pow(x,z) is done by
        !            28:
        !            29:     y=pow_ui(x,z) if z>0
        !            30:   else
        !            31:     y=1/pow_ui(x,z) if z<0
        !            32:  */
        !            33:
        !            34: int
        !            35: mpfr_pow_si (mpfr_ptr y, mpfr_srcptr x, long int n, mp_rnd_t rnd_mode)
        !            36: {
        !            37:   if (n > 0)
        !            38:     return mpfr_pow_ui(y, x, n, rnd_mode);
        !            39:   else
        !            40:     {
        !            41:       int inexact = 0;
        !            42:
        !            43:       if (MPFR_IS_NAN(x))
        !            44:         {
        !            45:           MPFR_SET_NAN(y);
        !            46:           MPFR_RET_NAN;
        !            47:         }
        !            48:
        !            49:       MPFR_CLEAR_NAN(y);
        !            50:
        !            51:       if (n == 0)
        !            52:         return mpfr_set_ui(y, 1, GMP_RNDN);
        !            53:
        !            54:       if (MPFR_IS_INF(x))
        !            55:         {
        !            56:           MPFR_SET_ZERO(y);
        !            57:           if (MPFR_SIGN(x) > 0 || ((unsigned) n & 1) == 0)
        !            58:             MPFR_SET_POS(y);
        !            59:           else
        !            60:             MPFR_SET_NEG(y);
        !            61:           MPFR_RET(0);
        !            62:         }
        !            63:
        !            64:       if (MPFR_IS_ZERO(x))
        !            65:         {
        !            66:           MPFR_SET_INF(y);
        !            67:           if (MPFR_SIGN(x) > 0 || ((unsigned) n & 1) == 0)
        !            68:             MPFR_SET_POS(y);
        !            69:           else
        !            70:             MPFR_SET_NEG(y);
        !            71:           MPFR_RET(0);
        !            72:         }
        !            73:
        !            74:       MPFR_CLEAR_INF(y);
        !            75:
        !            76:       n = -n;
        !            77:
        !            78:       /* General case */
        !            79:       {
        !            80:         /* Declaration of the intermediary variable */
        !            81:         mpfr_t t, ti;
        !            82:
        !            83:         /* Declaration of the size variable */
        !            84:         mp_prec_t Nx = MPFR_PREC(x);   /* Precision of input variable */
        !            85:         mp_prec_t Ny = MPFR_PREC(y);   /* Precision of input variable */
        !            86:
        !            87:         mp_prec_t Nt;   /* Precision of the intermediary variable */
        !            88:         long int err;  /* Precision of error */
        !            89:
        !            90:         /* compute the precision of intermediary variable */
        !            91:         Nt=MAX(Nx,Ny);
        !            92:         /* the optimal number of bits : see algorithms.ps */
        !            93:         Nt=Nt+3+_mpfr_ceil_log2(Nt);
        !            94:
        !            95:         /* initialise of intermediary  variable */
        !            96:         mpfr_init(t);
        !            97:         mpfr_init(ti);
        !            98:
        !            99:         do {
        !           100:
        !           101:           /* reactualisation of the precision */
        !           102:           mpfr_set_prec(t,Nt);
        !           103:           mpfr_set_prec(ti,Nt);
        !           104:
        !           105:           /* compute 1/(x^n) n>0*/
        !           106:           mpfr_pow_ui(ti,x,(unsigned long int)(n),GMP_RNDN);
        !           107:           mpfr_ui_div(t,1,ti,GMP_RNDN);
        !           108:
        !           109:           /* estimation of the error -- see pow function in algorithms.ps*/
        !           110:           err = Nt - 3;
        !           111:
        !           112:           /* actualisation of the precision */
        !           113:           Nt += 10;
        !           114:
        !           115:         } while (err<0 || !mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Ny));
        !           116:
        !           117:         inexact = mpfr_set(y,t,rnd_mode);
        !           118:         mpfr_clear(t);
        !           119:         mpfr_clear(ti);
        !           120:       }
        !           121:       return inexact;
        !           122:     }
        !           123: }
        !           124:
        !           125:
        !           126:
        !           127:
        !           128:
        !           129:
        !           130: