125c28e83SPiotr Jasiukajtis /*
225c28e83SPiotr Jasiukajtis * CDDL HEADER START
325c28e83SPiotr Jasiukajtis *
425c28e83SPiotr Jasiukajtis * The contents of this file are subject to the terms of the
525c28e83SPiotr Jasiukajtis * Common Development and Distribution License (the "License").
625c28e83SPiotr Jasiukajtis * You may not use this file except in compliance with the License.
725c28e83SPiotr Jasiukajtis *
825c28e83SPiotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
925c28e83SPiotr Jasiukajtis * or http://www.opensolaris.org/os/licensing.
1025c28e83SPiotr Jasiukajtis * See the License for the specific language governing permissions
1125c28e83SPiotr Jasiukajtis * and limitations under the License.
1225c28e83SPiotr Jasiukajtis *
1325c28e83SPiotr Jasiukajtis * When distributing Covered Code, include this CDDL HEADER in each
1425c28e83SPiotr Jasiukajtis * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
1525c28e83SPiotr Jasiukajtis * If applicable, add the following below this CDDL HEADER, with the
1625c28e83SPiotr Jasiukajtis * fields enclosed by brackets "[]" replaced with your own identifying
1725c28e83SPiotr Jasiukajtis * information: Portions Copyright [yyyy] [name of copyright owner]
1825c28e83SPiotr Jasiukajtis *
1925c28e83SPiotr Jasiukajtis * CDDL HEADER END
2025c28e83SPiotr Jasiukajtis */
2125c28e83SPiotr Jasiukajtis /*
2225c28e83SPiotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
2325c28e83SPiotr Jasiukajtis */
2425c28e83SPiotr Jasiukajtis /*
2525c28e83SPiotr Jasiukajtis * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
2625c28e83SPiotr Jasiukajtis * Use is subject to license terms.
2725c28e83SPiotr Jasiukajtis */
2825c28e83SPiotr Jasiukajtis
29*ddc0e0b5SRichard Lowe #pragma weak __cosh = cosh
3025c28e83SPiotr Jasiukajtis
3125c28e83SPiotr Jasiukajtis /* INDENT OFF */
3225c28e83SPiotr Jasiukajtis /*
3325c28e83SPiotr Jasiukajtis * cosh(x)
3425c28e83SPiotr Jasiukajtis * Code originated from 4.3bsd.
3525c28e83SPiotr Jasiukajtis * Modified by K.C. Ng for SUN 4.0 libm.
3625c28e83SPiotr Jasiukajtis * Method :
3725c28e83SPiotr Jasiukajtis * 1. Replace x by |x| (cosh(x) = cosh(-x)).
3825c28e83SPiotr Jasiukajtis * 2.
3925c28e83SPiotr Jasiukajtis * [ exp(x) - 1 ]^2
4025c28e83SPiotr Jasiukajtis * 0 <= x <= 0.3465 : cosh(x) := 1 + -------------------
4125c28e83SPiotr Jasiukajtis * 2*exp(x)
4225c28e83SPiotr Jasiukajtis *
4325c28e83SPiotr Jasiukajtis * exp(x) + 1/exp(x)
4425c28e83SPiotr Jasiukajtis * 0.3465 <= x <= 22 : cosh(x) := -------------------
4525c28e83SPiotr Jasiukajtis * 2
4625c28e83SPiotr Jasiukajtis * 22 <= x <= lnovft : cosh(x) := exp(x)/2
4725c28e83SPiotr Jasiukajtis * lnovft <= x < INF : cosh(x) := scalbn(exp(x-1024*ln2),1023)
4825c28e83SPiotr Jasiukajtis *
4925c28e83SPiotr Jasiukajtis * Note: .3465 is a number near one half of ln2.
5025c28e83SPiotr Jasiukajtis *
5125c28e83SPiotr Jasiukajtis * Special cases:
5225c28e83SPiotr Jasiukajtis * cosh(x) is |x| if x is +INF, -INF, or NaN.
5325c28e83SPiotr Jasiukajtis * only cosh(0)=1 is exact for finite x.
5425c28e83SPiotr Jasiukajtis */
5525c28e83SPiotr Jasiukajtis /* INDENT ON */
5625c28e83SPiotr Jasiukajtis
5725c28e83SPiotr Jasiukajtis #include "libm.h"
5825c28e83SPiotr Jasiukajtis
5925c28e83SPiotr Jasiukajtis static const double
6025c28e83SPiotr Jasiukajtis ln2 = 6.93147180559945286227e-01,
6125c28e83SPiotr Jasiukajtis ln2hi = 6.93147180369123816490e-01,
6225c28e83SPiotr Jasiukajtis ln2lo = 1.90821492927058770002e-10,
6325c28e83SPiotr Jasiukajtis lnovft = 7.09782712893383973096e+02;
6425c28e83SPiotr Jasiukajtis
6525c28e83SPiotr Jasiukajtis double
cosh(double x)6625c28e83SPiotr Jasiukajtis cosh(double x) {
6725c28e83SPiotr Jasiukajtis double t, w;
6825c28e83SPiotr Jasiukajtis
6925c28e83SPiotr Jasiukajtis w = fabs(x);
7025c28e83SPiotr Jasiukajtis if (!finite(w))
7125c28e83SPiotr Jasiukajtis return (w * w);
7225c28e83SPiotr Jasiukajtis if (w < 0.3465) {
7325c28e83SPiotr Jasiukajtis t = expm1(w);
7425c28e83SPiotr Jasiukajtis w = 1.0 + t;
7525c28e83SPiotr Jasiukajtis if (w != 1.0)
7625c28e83SPiotr Jasiukajtis w = 1.0 + (t * t) / (w + w);
7725c28e83SPiotr Jasiukajtis return (w);
7825c28e83SPiotr Jasiukajtis } else if (w < 22.0) {
7925c28e83SPiotr Jasiukajtis t = exp(w);
8025c28e83SPiotr Jasiukajtis return (0.5 * (t + 1.0 / t));
8125c28e83SPiotr Jasiukajtis } else if (w <= lnovft) {
8225c28e83SPiotr Jasiukajtis return (0.5 * exp(w));
8325c28e83SPiotr Jasiukajtis } else {
8425c28e83SPiotr Jasiukajtis w = (w - 1024 * ln2hi) - 1024 * ln2lo;
8525c28e83SPiotr Jasiukajtis if (w >= ln2)
8625c28e83SPiotr Jasiukajtis return (_SVID_libm_err(x, x, 5));
8725c28e83SPiotr Jasiukajtis else
8825c28e83SPiotr Jasiukajtis return (scalbn(exp(w), 1023));
8925c28e83SPiotr Jasiukajtis }
9025c28e83SPiotr Jasiukajtis }
91