25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * CDDL HEADER START
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * The contents of this file are subject to the terms of the
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Common Development and Distribution License (the "License").
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You may not use this file except in compliance with the License.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * or http://www.opensolaris.org/os/licensing.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * See the License for the specific language governing permissions
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * RETURN THE HYPERBOLIC COSINE OF X
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 1. Replace x by |x| (coshl(x) = coshl(-x)).
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * [ expl(x) - 1 ]^2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0 <= x <= 0.3465 : coshl(x) := 1 + -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * expl(x) + 1/expl(x)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0.3465 <= x <= thresh : coshl(x) := -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * thresh <= x <= lnovft : coshl(x) := expl(x)/2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * lnovft <= x < INF : coshl(x) := scalbnl(expl(x-1024*ln2),1023)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * thr1 a number that is near one half of ln2.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * thr2 a number such that
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * expl(thresh)+expl(-thresh)=expl(thresh)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * lnovft: logrithm of the overflow threshold
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * = MEP1*ln2 chopped to machine precision.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * ME maximum exponent
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * MEP1 maximum exponent plus 1
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Special cases:
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * coshl(x) is |x| if x is +INF, -INF, or NaN.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * only coshl(0)=1 is exact for finite x.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#define LNOVFT 1.135652340629414394949193107797076342845e+4L
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis /* last 32 bits of LN2HI is zero */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#define LN2HI 6.931471805599453094172319547495844850203e-0001L
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis#define LN2LO 1.667085920830552208890449330400379754169e-0025L
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisstatic const long double
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis long double t, w;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (w + w); /* x is INF or NaN */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis w = one + (t * t) / (w + w);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if (w < thr2) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if (w <= lnovftL)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (scalbnl(expl((w - MEP1 * ln2hi) - MEP1 * ln2lo), ME));