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author | Igor Pashev <pashev.igor@gmail.com> | 2012-09-11 19:12:10 +0400 |
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committer | Igor Pashev <pashev.igor@gmail.com> | 2012-09-11 19:12:10 +0400 |
commit | 19700b860d9ec70d01e885d92c3d4f62fd052873 (patch) | |
tree | b6b265cd81fb97b4675f4a285f397479609fdf18 /usr/src/libm/src/Q/coshl.c | |
download | libm-upstream.tar.gz |
Imported Upstream version 20060131HEADupstream/20060131upstreammaster
Diffstat (limited to 'usr/src/libm/src/Q/coshl.c')
-rw-r--r-- | usr/src/libm/src/Q/coshl.c | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/usr/src/libm/src/Q/coshl.c b/usr/src/libm/src/Q/coshl.c new file mode 100644 index 0000000..966a9a4 --- /dev/null +++ b/usr/src/libm/src/Q/coshl.c @@ -0,0 +1,104 @@ +/* + * CDDL HEADER START + * + * The contents of this file are subject to the terms of the + * Common Development and Distribution License (the "License"). + * You may not use this file except in compliance with the License. + * + * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE + * or http://www.opensolaris.org/os/licensing. + * See the License for the specific language governing permissions + * and limitations under the License. + * + * When distributing Covered Code, include this CDDL HEADER in each + * file and include the License file at usr/src/OPENSOLARIS.LICENSE. + * If applicable, add the following below this CDDL HEADER, with the + * fields enclosed by brackets "[]" replaced with your own identifying + * information: Portions Copyright [yyyy] [name of copyright owner] + * + * CDDL HEADER END + */ + +/* + * Copyright 2006 Sun Microsystems, Inc. All rights reserved. + * Use is subject to license terms. + */ + +#pragma ident "@(#)coshl.c 1.8 06/01/31 SMI" + +#pragma weak coshl = __coshl + +#include "libm.h" + +/* + * coshl(X) + * RETURN THE HYPERBOLIC COSINE OF X + * + * Method : + * 1. Replace x by |x| (coshl(x) = coshl(-x)). + * 2. + * [ expl(x) - 1 ]^2 + * 0 <= x <= 0.3465 : coshl(x) := 1 + ------------------- + * 2*expl(x) + * + * expl(x) + 1/expl(x) + * 0.3465 <= x <= thresh : coshl(x) := ------------------- + * 2 + * thresh <= x <= lnovft : coshl(x) := expl(x)/2 + * lnovft <= x < INF : coshl(x) := scalbnl(expl(x-1024*ln2),1023) + * + * here + * thr1 a number that is near one half of ln2. + * thr2 a number such that + * expl(thresh)+expl(-thresh)=expl(thresh) + * lnovft: logrithm of the overflow threshold + * = MEP1*ln2 chopped to machine precision. + * ME maximum exponent + * MEP1 maximum exponent plus 1 + * + * Special cases: + * coshl(x) is |x| if x is +INF, -INF, or NaN. + * only coshl(0)=1 is exact for finite x. + */ + +#define ME 16383 +#define MEP1 16384 +#define LNOVFT 1.135652340629414394949193107797076342845e+4L + /* last 32 bits of LN2HI is zero */ +#define LN2HI 6.931471805599453094172319547495844850203e-0001L +#define LN2LO 1.667085920830552208890449330400379754169e-0025L +#define THR1 0.3465L +#define THR2 45.L + +static const long double + half = 0.5L, + tinyl = 7.5e-37L, + one = 1.0L, + ln2hi = LN2HI, + ln2lo = LN2LO, + lnovftL = LNOVFT, + thr1 = THR1, + thr2 = THR2; + +long double +coshl(long double x) { + long double t, w; + + w = fabsl(x); + if (!finitel(w)) + return (w + w); /* x is INF or NaN */ + if (w < thr1) { + t = w < tinyl ? w : expm1l(w); + w = one + t; + if (w != one) + w = one + (t * t) / (w + w); + return (w); + } else if (w < thr2) { + t = expl(w); + return (half * (t + one / t)); + } else if (w <= lnovftL) + return (half * expl(w)); + else { + return (scalbnl(expl((w - MEP1 * ln2hi) - MEP1 * ln2lo), ME)); + } +} |