diff options
Diffstat (limited to 'sysdeps/powerpc/powerpc64/power4/fpu/slowpow.c')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/power4/fpu/slowpow.c | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/sysdeps/powerpc/powerpc64/power4/fpu/slowpow.c b/sysdeps/powerpc/powerpc64/power4/fpu/slowpow.c new file mode 100644 index 0000000000..ad147a89a6 --- /dev/null +++ b/sysdeps/powerpc/powerpc64/power4/fpu/slowpow.c @@ -0,0 +1,94 @@ +/* + * IBM Accurate Mathematical Library + * written by International Business Machines Corp. + * Copyright (C) 2001, 2006 Free Software Foundation + * + * 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, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + */ +/*************************************************************************/ +/* MODULE_NAME:slowpow.c */ +/* */ +/* FUNCTION:slowpow */ +/* */ +/*FILES NEEDED:mpa.h */ +/* mpa.c mpexp.c mplog.c halfulp.c */ +/* */ +/* Given two IEEE double machine numbers y,x , routine computes the */ +/* correctly rounded (to nearest) value of x^y. Result calculated by */ +/* multiplication (in halfulp.c) or if result isn't accurate enough */ +/* then routine converts x and y into multi-precision doubles and */ +/* recompute. */ +/*************************************************************************/ + +#include "mpa.h" +#include "math_private.h" + +void __mpexp (mp_no * x, mp_no * y, int p); +void __mplog (mp_no * x, mp_no * y, int p); +double ulog (double); +double __halfulp (double x, double y); + +double +__slowpow (double x, double y, double z) +{ + double res, res1; + long double ldw, ldz, ldpp; + static const long double ldeps = 0x4.0p-96; + + res = __halfulp (x, y); /* halfulp() returns -10 or x^y */ + if (res >= 0) + return res; /* if result was really computed by halfulp */ + /* else, if result was not really computed by halfulp */ + + /* Compute pow as long double, 106 bits */ + ldz = __ieee754_logl ((long double) x); + ldw = (long double) y *ldz; + ldpp = __ieee754_expl (ldw); + res = (double) (ldpp + ldeps); + res1 = (double) (ldpp - ldeps); + + if (res != res1) /* if result still not accurate enough */ + { /* use mpa for higher persision. */ + mp_no mpx, mpy, mpz, mpw, mpp, mpr, mpr1; + static const mp_no eps = { -3, {1.0, 4.0} }; + int p; + + p = 10; /* p=precision 240 bits */ + __dbl_mp (x, &mpx, p); + __dbl_mp (y, &mpy, p); + __dbl_mp (z, &mpz, p); + __mplog (&mpx, &mpz, p); /* log(x) = z */ + __mul (&mpy, &mpz, &mpw, p); /* y * z =w */ + __mpexp (&mpw, &mpp, p); /* e^w =pp */ + __add (&mpp, &eps, &mpr, p); /* pp+eps =r */ + __mp_dbl (&mpr, &res, p); + __sub (&mpp, &eps, &mpr1, p); /* pp -eps =r1 */ + __mp_dbl (&mpr1, &res1, p); /* converting into double precision */ + if (res == res1) + return res; + + /* if we get here result wasn't calculated exactly, continue for + more exact calculation using 768 bits. */ + p = 32; + __dbl_mp (x, &mpx, p); + __dbl_mp (y, &mpy, p); + __dbl_mp (z, &mpz, p); + __mplog (&mpx, &mpz, p); /* log(c)=z */ + __mul (&mpy, &mpz, &mpw, p); /* y*z =w */ + __mpexp (&mpw, &mpp, p); /* e^w=pp */ + __mp_dbl (&mpp, &res, p); /* converting into double precision */ + } + return res; +} |