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Diffstat (limited to 'regress/lib/libc/cephes/elog.c')
-rw-r--r-- | regress/lib/libc/cephes/elog.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/regress/lib/libc/cephes/elog.c b/regress/lib/libc/cephes/elog.c new file mode 100644 index 00000000000..079cc754f48 --- /dev/null +++ b/regress/lib/libc/cephes/elog.c @@ -0,0 +1,110 @@ +/* $OpenBSD: elog.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. + */ + +/* xlog.c */ +/* natural logarithm */ +/* by Stephen L. Moshier. */ + +#include "mconf.h" +#include "ehead.h" + + + +void elog( x, y ) +unsigned short *x, *y; +{ +unsigned short xx[NE], z[NE], a[NE], b[NE], t[NE], qj[NE]; +long ex; +int fex; + + +if( x[NE-1] & (unsigned short )0x8000 ) + { + eclear(y); + mtherr( "elog", DOMAIN ); + return; + } +if( ecmp( x, ezero ) == 0 ) + { + einfin( y ); + eneg(y); + mtherr( "elog", SING ); + return; + } +if( ecmp( x, eone ) == 0 ) + { + eclear( y ); + return; + } + +/* range reduction: log x = log( 2**ex * m ) = ex * log2 + log m */ +efrexp( x, &fex, xx ); +/* +emov(x, xx ); +ex = xx[NX-1] & 0x7fff; +ex -= 0x3ffe; +xx[NX-1] = 0x3ffe; +*/ + +/* Adjust range to 1/sqrt(2), sqrt(2) */ +esqrt2[NE-1] -= 1; +if( ecmp( xx, esqrt2 ) < 0 ) + { + fex -= 1; + emul( xx, etwo, xx ); + } +esqrt2[NE-1] += 1; + +esub( eone, xx, a ); +if( a[NE-1] == 0 ) + { + eclear( y ); + goto logdon; + } +eadd( eone, xx, b ); +ediv( b, a, y ); /* store (x-1)/(x+1) in y */ + +emul( y, y, z ); + +emov( eone, a ); +emov( eone, b ); +emov( eone, qj ); +do + { + eadd( etwo, qj, qj ); /* 2 * i + 1 */ + emul( z, a, a ); + ediv( qj, a, t ); + eadd( t, b, b ); + } +while( ((b[NE-1] & 0x7fff) - (t[NE-1] & 0x7fff)) < NBITS ); + + +emul( b, y, y ); +emul( y, etwo, y ); + +logdon: + +/* now add log of 2**ex */ +if( fex != 0 ) + { + ex = fex; + ltoe( &ex, b ); + emul( elog2, b, b ); + eadd( b, y, y ); + } +} |