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

1.1     ! ohara       1: /* mpfr_pow_ui-- compute the power of a floating-point
        !             2:                                   by a machine integer
        !             3:
        !             4: Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
        !             5:
        !             6: This file is part of the MPFR Library.
        !             7:
        !             8: The MPFR Library is free software; you can redistribute it and/or modify
        !             9: it under the terms of the GNU Lesser General Public License as published by
        !            10: the Free Software Foundation; either version 2.1 of the License, or (at your
        !            11: option) any later version.
        !            12:
        !            13: The MPFR Library is distributed in the hope that it will be useful, but
        !            14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
        !            15: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
        !            16: License for more details.
        !            17:
        !            18: You should have received a copy of the GNU Lesser General Public License
        !            19: along with the MPFR Library; see the file COPYING.LIB.  If not, write to
        !            20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
        !            21: MA 02111-1307, USA. */
        !            22:
        !            23: #include "gmp.h"
        !            24: #include "mpfr.h"
        !            25: #include "mpfr-impl.h"
        !            26:
        !            27: /* sets x to y^n, and return 0 if exact, non-zero otherwise */
        !            28: int
        !            29: mpfr_pow_ui (mpfr_ptr x, mpfr_srcptr y, unsigned long int n, mp_rnd_t rnd)
        !            30: {
        !            31:   long int i, err;
        !            32:   unsigned long m;
        !            33:   mpfr_t res;
        !            34:   mp_prec_t prec;
        !            35:   int inexact;
        !            36:   mp_rnd_t rnd1;
        !            37:
        !            38:   if (MPFR_IS_NAN(y))
        !            39:     {
        !            40:       MPFR_SET_NAN(x);
        !            41:       MPFR_RET_NAN;
        !            42:     }
        !            43:
        !            44:   MPFR_CLEAR_NAN(x);
        !            45:
        !            46:   if (n == 0) /* x^0 = 1 for any x */
        !            47:     {
        !            48:       /* The return mpfr_set_ui is important as 1 isn't necessarily
        !            49:          in the exponent range. */
        !            50:       return mpfr_set_ui (x, 1, rnd);
        !            51:     }
        !            52:
        !            53:   if (MPFR_IS_INF(y))
        !            54:     {
        !            55:       /* Inf^n = Inf, (-Inf)^n = Inf for n even, -Inf for n odd */
        !            56:       if ((MPFR_SIGN(y) < 0) && (n % 2 == 1))
        !            57:         MPFR_SET_NEG(x);
        !            58:       else
        !            59:         MPFR_SET_POS(x);
        !            60:       MPFR_SET_INF(x);
        !            61:       MPFR_RET(0);
        !            62:     }
        !            63:
        !            64:   MPFR_CLEAR_INF(x);
        !            65:
        !            66:   mpfr_init (res);
        !            67:
        !            68:   prec = MPFR_PREC(x);
        !            69:
        !            70:   rnd1 = (MPFR_SIGN(y) > 0) ? GMP_RNDU : GMP_RNDD; /* away */
        !            71:
        !            72:   do
        !            73:     {
        !            74:       prec += 3;
        !            75:       for (m=n, i=0; m; i++, m>>=1, prec++);
        !            76:       mpfr_set_prec (res, prec);
        !            77:       inexact = mpfr_set (res, y, rnd1);
        !            78:       err = 1;
        !            79:       /* now 2^(i-1) <= n < 2^i */
        !            80:       for (i-=2; i>=0; i--)
        !            81:        {
        !            82:          if (mpfr_mul (res, res, res, GMP_RNDU))
        !            83:            inexact = 1;
        !            84:          err++;
        !            85:          if (n & (1 << i))
        !            86:            if (mpfr_mul (res, res, y, rnd1))
        !            87:              inexact = 1;
        !            88:        }
        !            89:       err = prec - err;
        !            90:       if (err < 0)
        !            91:        err = 0;
        !            92:     }
        !            93:   while (inexact && (mpfr_can_round (res, err,
        !            94:          (MPFR_SIGN(res) > 0) ? GMP_RNDU : GMP_RNDD, rnd, MPFR_PREC(x)) == 0));
        !            95:
        !            96:   if (mpfr_set (x, res, rnd))
        !            97:     inexact = 1;
        !            98:
        !            99:   mpfr_clear (res);
        !           100:
        !           101:   return inexact;
        !           102: }
        !           103: