mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-25 20:21:07 +00:00
102 lines
3.2 KiB
C
102 lines
3.2 KiB
C
/*
|
|
* IBM Accurate Mathematical Library
|
|
* written by International Business Machines Corp.
|
|
* Copyright (C) 2001-2013 Free Software Foundation, Inc.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU Lesser General Public License as published by
|
|
* the Free Software Foundation; either version 2.1 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program 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 Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public License
|
|
* along with this program; if not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
/******************************************************************/
|
|
/* */
|
|
/* MODULE_NAME:mpatan.c */
|
|
/* */
|
|
/* FUNCTIONS:mpatan */
|
|
/* */
|
|
/* FILES NEEDED: mpa.h endian.h mpatan.h */
|
|
/* mpa.c */
|
|
/* */
|
|
/* Multi-Precision Atan function subroutine, for precision p >= 4.*/
|
|
/* The relative error of the result is bounded by 34.32*r**(1-p), */
|
|
/* where r=2**24. */
|
|
/******************************************************************/
|
|
|
|
#include "endian.h"
|
|
#include "mpa.h"
|
|
|
|
#ifndef SECTION
|
|
# define SECTION
|
|
#endif
|
|
|
|
#include "mpatan.h"
|
|
|
|
void __mpsqrt(mp_no *, mp_no *, int);
|
|
|
|
void
|
|
SECTION
|
|
__mpatan(mp_no *x, mp_no *y, int p) {
|
|
|
|
int i,m,n;
|
|
double dx;
|
|
mp_no
|
|
mptwoim1 = {0,{0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
|
|
0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,
|
|
0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0}};
|
|
|
|
mp_no mps,mpsm,mpt,mpt1,mpt2,mpt3;
|
|
|
|
/* Choose m and initiate mptwoim1 */
|
|
if (EX>0) m=7;
|
|
else if (EX<0) m=0;
|
|
else {
|
|
__mp_dbl(x,&dx,p); dx=ABS(dx);
|
|
for (m=6; m>0; m--)
|
|
{if (dx>__atan_xm[m].d) break;}
|
|
}
|
|
mptwoim1.e = 1;
|
|
mptwoim1.d[0] = ONE;
|
|
|
|
/* Reduce x m times */
|
|
__mul(x,x,&mpsm,p);
|
|
if (m==0) __cpy(x,&mps,p);
|
|
else {
|
|
for (i=0; i<m; i++) {
|
|
__add(&mpone,&mpsm,&mpt1,p);
|
|
__mpsqrt(&mpt1,&mpt2,p);
|
|
__add(&mpt2,&mpt2,&mpt1,p);
|
|
__add(&mptwo,&mpsm,&mpt2,p);
|
|
__add(&mpt1,&mpt2,&mpt3,p);
|
|
__dvd(&mpsm,&mpt3,&mpt1,p);
|
|
__cpy(&mpt1,&mpsm,p);
|
|
}
|
|
__mpsqrt(&mpsm,&mps,p); mps.d[0] = X[0];
|
|
}
|
|
|
|
/* Evaluate a truncated power series for Atan(s) */
|
|
n=__atan_np[p]; mptwoim1.d[1] = __atan_twonm1[p].d;
|
|
__dvd(&mpsm,&mptwoim1,&mpt,p);
|
|
for (i=n-1; i>1; i--) {
|
|
mptwoim1.d[1] -= TWO;
|
|
__dvd(&mpsm,&mptwoim1,&mpt1,p);
|
|
__mul(&mpsm,&mpt,&mpt2,p);
|
|
__sub(&mpt1,&mpt2,&mpt,p);
|
|
}
|
|
__mul(&mps,&mpt,&mpt1,p);
|
|
__sub(&mps,&mpt1,&mpt,p);
|
|
|
|
/* Compute Atan(x) */
|
|
mptwoim1.d[1] = 1 << m;
|
|
__mul(&mptwoim1,&mpt,y,p);
|
|
|
|
return;
|
|
}
|