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

1.1     ! ohara       1: /* mpfr_hypot -- Euclidean distance
        !             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 <stdio.h>
        !            23: #include <stdlib.h>
        !            24: #include "gmp.h"
        !            25: #include "gmp-impl.h"
        !            26: #include "mpfr.h"
        !            27: #include "mpfr-impl.h"
        !            28:
        !            29:  /* The computation of hypot of x and y is done by
        !            30:
        !            31:     hypot(x,y)= sqrt(x^2+y^2) = z
        !            32:  */
        !            33:
        !            34: int
        !            35: mpfr_hypot (mpfr_ptr z, mpfr_srcptr x ,mpfr_srcptr y , mp_rnd_t rnd_mode)
        !            36: {
        !            37:   int inexact;
        !            38:   /* Flag calcul exacte */
        !            39:   int not_exact=0;
        !            40:
        !            41:   /* particular cases */
        !            42:
        !            43:   if (MPFR_IS_NAN(x) || MPFR_IS_NAN(y))
        !            44:     {
        !            45:       MPFR_SET_NAN(z);
        !            46:       MPFR_RET_NAN;
        !            47:     }
        !            48:
        !            49:   MPFR_CLEAR_NAN(z);
        !            50:
        !            51:   if (MPFR_IS_INF(x) || MPFR_IS_INF(y))
        !            52:     {
        !            53:       MPFR_SET_INF(z);
        !            54:       MPFR_SET_POS(z);
        !            55:       MPFR_RET(0);
        !            56:     }
        !            57:
        !            58:   MPFR_CLEAR_INF(z);
        !            59:
        !            60:   if(MPFR_IS_ZERO(x))
        !            61:     return mpfr_abs (z, y, rnd_mode);
        !            62:
        !            63:   if(MPFR_IS_ZERO(y))
        !            64:     return mpfr_abs (z, x, rnd_mode);
        !            65:
        !            66:   /* General case */
        !            67:
        !            68:   {
        !            69:     /* Declaration of the intermediary variable */
        !            70:     mpfr_t t, te,ti;
        !            71:     /* Declaration of the size variable */
        !            72:     mp_prec_t Nx = MPFR_PREC(x);   /* Precision of input variable */
        !            73:     mp_prec_t Ny = MPFR_PREC(y);   /* Precision of input variable */
        !            74:     mp_prec_t Nz = MPFR_PREC(z);   /* Precision of input variable */
        !            75:
        !            76:     int  Nt;   /* Precision of the intermediary variable */
        !            77:     long int err;  /* Precision of error */
        !            78:
        !            79:     /* compute the precision of intermediary variable */
        !            80:     Nt=MAX(MAX(Nx,Ny),Nz);
        !            81:
        !            82:     /* compute the size of intermediary variable -- see algorithms.ps */
        !            83:     Nt=Nt+2+_mpfr_ceil_log2(Nt);
        !            84:
        !            85:     /* initialise the intermediary variables */
        !            86:     mpfr_init(t);
        !            87:     mpfr_init(te);
        !            88:     mpfr_init(ti);
        !            89:
        !            90:     /* Hypot */
        !            91:     do {
        !            92:       not_exact=0;
        !            93:       /* reactualisation of the precision */
        !            94:       mpfr_set_prec(t,Nt);
        !            95:       mpfr_set_prec(te,Nt);
        !            96:       mpfr_set_prec(ti,Nt);
        !            97:
        !            98:       /* computations of hypot */
        !            99:       if(mpfr_mul(te,x,x,GMP_RNDN))   /* x^2 */
        !           100:         not_exact=1;
        !           101:
        !           102:       if(mpfr_mul(ti,y,y,GMP_RNDN))   /* y^2 */
        !           103:         not_exact=1;
        !           104:
        !           105:       if(mpfr_add(t,te,ti,GMP_RNDD))  /*x^2+y^2*/
        !           106:         not_exact=1;
        !           107:
        !           108:       if(mpfr_sqrt(t,t,GMP_RNDN))     /* sqrt(x^2+y^2)*/
        !           109:         not_exact=1;
        !           110:
        !           111:       /* estimation of the error */
        !           112:       err=Nt-(2);
        !           113:
        !           114:       Nt += 10;
        !           115:       if(Nt<0)Nt=0;
        !           116:
        !           117:     } while ((err <0) || ((!mpfr_can_round(t,err,GMP_RNDN,rnd_mode,Nz)) && not_exact));
        !           118:
        !           119:     inexact = mpfr_set (z, t, rnd_mode);
        !           120:     mpfr_clear(t);
        !           121:     mpfr_clear(ti);
        !           122:     mpfr_clear(te);
        !           123:
        !           124:   }
        !           125:
        !           126:   if (not_exact == 0 && inexact == 0)
        !           127:     return 0;
        !           128:
        !           129:   if (not_exact != 0 && inexact == 0)
        !           130:     return 1;
        !           131:
        !           132:   return inexact;
        !           133: }