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

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: }