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Diffstat (limited to 'regress/lib/libc/cephes/eexp.c')
-rw-r--r-- | regress/lib/libc/cephes/eexp.c | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/regress/lib/libc/cephes/eexp.c b/regress/lib/libc/cephes/eexp.c new file mode 100644 index 00000000000..74f0d6adb33 --- /dev/null +++ b/regress/lib/libc/cephes/eexp.c @@ -0,0 +1,86 @@ +/* $OpenBSD: eexp.c,v 1.1 2011/07/02 18:11:01 martynas Exp $ */ + +/* + * Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +/* xexp.c */ +/* exponential function check routine */ +/* by Stephen L. Moshier. */ + + +#include "ehead.h" + +void eexp( x, y ) +unsigned short *x, *y; +{ +unsigned short num[NE], den[NE], x2[NE]; +long i; +unsigned short sign, expchk; + +/* range reduction theory: x = i + f, 0<=f<1; + * e**x = e**i * e**f + * e**i = 2**(i/log 2). + * Let i/log2 = i1 + f1, 0<=f1<1. + * Then e**i = 2**i1 * 2**f1, so + * e**x = 2**i1 * e**(log 2 * f1) * e**f. + */ +if( ecmp(x, ezero) == 0 ) + { + emov( eone, y ); + return; + } +emov(x, x2); +expchk = x2[NE-1]; +sign = expchk & 0x8000; +x2[NE-1] &= 0x7fff; + +/* Test for excessively large argument */ +expchk &= 0x7fff; +if( expchk > (EXONE + 15) ) + { + eclear( y ); + if( sign == 0 ) + einfin( y ); + return; + } + +eifrac( x2, &i, num ); /* x = i + f */ + +if( i != 0 ) + { + ltoe( &i, den ); /* floating point i */ + ediv( elog2, den, den ); /* i/log 2 */ + eifrac( den, &i, den ); /* i/log 2 = i1 + f1 */ + emul( elog2, den, den ); /* log 2 * f1 */ + eadd( den, num, x2 ); /* log 2 * f1 + f */ + } + +/*x2[NE-1] -= 1;*/ +eldexp( x2, -1L, x2 ); /* divide by 2 */ +etanh( x2, x2 ); /* tanh( x/2 ) */ +eadd( x2, eone, num ); /* 1 + tanh */ +eneg( x2 ); +eadd( x2, eone, den ); /* 1 - tanh */ +ediv( den, num, y ); /* (1 + tanh)/(1 - tanh) */ + +/*y[NE-1] += i;*/ +if( sign ) + { + ediv( y, eone, y ); + i = -i; + } +eldexp( y, i, y ); /* multiply by 2**i */ +} |