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/* mpfr_agm -- arithmetic-geometric mean of two floating-point numbers
Copyright (C) 1999 PolKA project, Inria Lorraine and Loria
This file is part of the MPFR Library.
The MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include <stdio.h>
#include <math.h>
#include "gmp.h"
#include "gmp-impl.h"
#include "mpfr.h"
/*Memory gestion */
#define MON_INIT(xp, x, p, s) xp = (mp_ptr) TMP_ALLOC(s*BYTES_PER_MP_LIMB); x -> _mp_prec = p; x -> _mp_d = xp; x -> _mp_size = s; x -> _mp_exp = 0;
void
#ifdef __STDC__
mpfr_agm(mpfr_ptr r, mpfr_srcptr op2, mpfr_srcptr op1, mp_rnd_t rnd_mode)
#else
mpfr_agm(r, a, b, rnd_mode)
mpfr_ptr r;
mpfr_srcptr a;
mpfr_srcptr b;
mp_rnd_t rnd_mode;
#endif
{
int s, go_on;
mp_prec_t p, q;
double uo, vo;
mp_limb_t *up, *vp, *tmpp, *tmpup, *tmpvp, *ap, *bp;
mpfr_t u, v, tmp, tmpu, tmpv, a, b;
TMP_DECL(marker1);
TMP_DECL(marker2);
/* If a or b is NaN, the result is NaN */
if (FLAG_NAN(op1) || FLAG_NAN(op2))
{ SET_NAN(r); return; }
/* If a or b is negative, the result is NaN */
if ((MPFR_SIGN(op1) < 0) || (MPFR_SIGN(op2) < 0))
{ SET_NAN(r); return; }
/* If a or b is 0, the result is 0 */
if ((NOTZERO(op1) && NOTZERO(op2)) == 0)
{ SET_ZERO(r);
return;
}
/* precision of the following calculus */
q = PREC(r);
p = q + 15;
/* Initialisations */
go_on=1;
TMP_MARK(marker1);
s=(p-1)/BITS_PER_MP_LIMB+1;
MON_INIT(ap, a, p, s);
MON_INIT(bp, b, p, s);
TMP_MARK(marker2);
MON_INIT(up, u, p, s);
MON_INIT(vp, v, p, s);
MON_INIT(tmpup, tmpu, p, s);
MON_INIT(tmpvp, tmpv, p, s);
MON_INIT(tmpp, tmp, p, s);
/* b and a will be the 2 operands but I want b>= a */
if (mpfr_cmp(op1,op2) > 0) {
mpfr_set(b,op1,GMP_RNDN); mpfr_set(a,op2,GMP_RNDN);
}
else {
mpfr_set(b,op2,GMP_RNDN); mpfr_set(a,op1,GMP_RNDN);
}
vo=mpfr_get_d(b);
uo=mpfr_get_d(a);
mpfr_set(u,a,GMP_RNDN);
mpfr_set(v,b,GMP_RNDN);
/* Main loop */
while (go_on) {
int err, eq, can_round;
eq=0;
err=ceil((3.0/2.0*log((double)p)/log(2.0)+1.0)*exp(-(double)p*log(2.0))+3.0*exp(-2.0*(double)p*uo*log(2.0)/(vo-uo)));
if(p-err-3<=q) {
p=q+err+4;
err=ceil((3.0/2.0*log((double)p)/log(2.0)+1.0)*exp(-(double)p*log(2.0))+3.0*exp(-2.0*(double)p*uo*log(2.0)/(vo-uo)));
}
/* Calculus of un and vn */
while (eq<=p-2) {
mpfr_mul(tmp,u,v,GMP_RNDN);
mpfr_sqrt(tmpu,tmp,GMP_RNDN);
mpfr_add(tmp,u,v,GMP_RNDN);
mpfr_div_2exp(tmpv,tmp,1,GMP_RNDN);
mpfr_set(u,tmpu,GMP_RNDN);
mpfr_set(v,tmpv,GMP_RNDN);
if (mpfr_cmp(v,u)>=0)
eq=mpfr_cmp2(v,u);
else
eq=mpfr_cmp2(u,v);
}
/* printf("avant can_round %i bits faux\n v : ",err+3);
mpfr_print_raw(v); printf("\n u : ");
mpfr_print_raw(u);printf("\n");*/
/* Roundability of the result */
can_round=mpfr_can_round(v,p-err-3,GMP_RNDN,rnd_mode,q);
if (can_round)
go_on=0;
else {
go_on=1;
p+=5;
TMP_FREE(marker2);
TMP_MARK(marker2);
s=(p-1)/BITS_PER_MP_LIMB+1;
MON_INIT(up, u, p, s);
MON_INIT(vp, v, p, s);
MON_INIT(tmpup, tmpu, p, s);
MON_INIT(tmpvp, tmpv, p, s);
MON_INIT(tmpp, tmp, p, s);
mpfr_set(u,a,GMP_RNDN);
mpfr_set(v,b,GMP_RNDN);
}
}
/* End of while */
/* Setting of the result */
mpfr_set(r,v,rnd_mode);
/* Let's clean */
TMP_FREE(marker1);
return ;
}
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