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
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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| (COSH(x) = COSH(-x)).
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * [ EXP(x) - 1 ]^2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0 <= x <= 0.3465 : COSH(x) := 1 + -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * EXP(x) + 1/EXP(x)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0.3465 <= x <= thresh : COSH(x) := -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * thresh <= x <= lnovft : COSH(x) := EXP(x)/2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * lnovft <= x < INF : COSH(x) := SCALBN(EXP(x-MEP1*ln2),ME)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0.3465 a number that is near one half of ln2.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * thresh a number such that
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * EXP(thresh)+EXP(-thresh)=EXP(thresh)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * lnovft logarithm 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 * COSH(x) is |x| if x is +INF, -INF, or NaN.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * only COSH(0)=1 is exact for finite x.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisstatic const long double C[] = {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 1.135652340629414394879149e+04L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 7.004447686242549087858985e-16L,
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis 2.710505431213761085018632e-20L, /* 2^-65 */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis long double w, t;
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (w + w); /* x is INF or NaN */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (one + w); /* inexact+directed rounding */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis w = one + (t * t) / (w + w);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (scalbnl(expl((w - lnovft) - lnovlo), 16383));