Return to pow_si.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpfr

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

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: