Return to factorial.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpfr

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

1.1     ! ohara       1: /* mpfr_fac_ui -- factorial of a non-negative integer
        !             2:
        !             3: Copyright 2001 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 n! is done by
        !            28:
        !            29:     n!=prod^{n}_{i=1}i
        !            30:  */
        !            31:
        !            32: int
        !            33: mpfr_fac_ui (mpfr_ptr y, unsigned long int x , mp_rnd_t rnd_mode)
        !            34: {
        !            35:
        !            36:   /****** Declaration ******/
        !            37:
        !            38:     mpfr_t t;       /* Variable of Intermediary Calculation*/
        !            39:     int i;
        !            40:     int round, inexact = 0;
        !            41:     int boucle = 1;
        !            42:
        !            43:     mp_prec_t Ny;   /* Precision of output variable */
        !            44:     mp_prec_t Nt;   /* Precision of Intermediary Calculation variable */
        !            45:     mp_prec_t err;  /* Precision of error */
        !            46:
        !            47:   /***** test x = 0  ******/
        !            48:
        !            49:     if (x == 0)
        !            50:       {
        !            51:        mpfr_set_ui (y, 1, GMP_RNDN); /* 0! = 1 */
        !            52:        return 0;
        !            53:       }
        !            54:     else
        !            55:       {
        !            56:         /* Initialisation of the Precision */
        !            57:        Ny=MPFR_PREC(y);
        !            58:
        !            59:        Nt=Ny+2*(int)_mpfr_ceil_log2((double)x)+10; /*compute the size of intermediary variable */
        !            60:
        !            61:
        !            62:         mpfr_init2(t, Nt);/* initialise of intermediary variable */
        !            63:
        !            64:         while (boucle)
        !            65:           {
        !            66:             inexact = mpfr_set_ui (t, 1, GMP_RNDZ);
        !            67:
        !            68:             for(i=2;i<=x;i++)              /* compute factorial */
        !            69:               {
        !            70:                 round = mpfr_mul_ui (t, t, i, GMP_RNDZ);
        !            71:                 /* assume the first inexact product gives the sign
        !            72:                    of difference: is that always correct? */
        !            73:                 if (inexact == 0)
        !            74:                   inexact = round;
        !            75:               }
        !            76:
        !            77:             err = Nt - 1 - (int) _mpfr_ceil_log2 ((double) Nt);
        !            78:
        !            79:             round = !inexact || mpfr_can_round (t,err,GMP_RNDZ,rnd_mode,Ny);
        !            80:
        !            81:             if (round)
        !            82:               {
        !            83:                 round = mpfr_set (y, t, rnd_mode);
        !            84:                  if (inexact == 0)
        !            85:                     inexact = round;
        !            86:                  boucle=0;
        !            87:                }
        !            88:              else
        !            89:                {
        !            90:                  Nt=Nt+10;
        !            91:                  /*initialise of intermediary variable */
        !            92:                  mpfr_set_prec(t, Nt);
        !            93:                }
        !            94:          }
        !            95:
        !            96:          mpfr_clear(t);
        !            97:           return inexact;
        !            98:
        !            99:     }
        !           100: }
        !           101:
        !           102:
        !           103:
        !           104: