1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 24 */ 25 /* 26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 27 * Use is subject to license terms. 28 */ 29 30 #if defined(ELFOBJ) 31 #pragma weak tanhl = __tanhl 32 #endif 33 34 /* 35 * tanhl(x) returns the hyperbolic tangent of x 36 * 37 * Method : 38 * 1. reduce x to non-negative: tanhl(-x) = - tanhl(x). 39 * 2. 40 * 0 < x <= small : tanhl(x) := x 41 * -expm1l(-2x) 42 * small < x <= 1 : tanhl(x) := -------------- 43 * expm1l(-2x) + 2 44 * 2 45 * 1 <= x <= threshold : tanhl(x) := 1 - --------------- 46 * expm1l(2x) + 2 47 * threshold < x <= INF : tanhl(x) := 1. 48 * 49 * where 50 * single : small = 1.e-5 threshold = 11.0 51 * double : small = 1.e-10 threshold = 22.0 52 * quad : small = 1.e-20 threshold = 45.0 53 * 54 * Note: threshold was chosen so that 55 * fl(1.0+2/(expm1(2*threshold)+2)) == 1. 56 * 57 * Special cases: 58 * tanhl(NaN) is NaN; 59 * only tanhl(0.0)=0.0 is exact for finite argument. 60 */ 61 62 #include "libm.h" 63 #include "longdouble.h" 64 65 static const long double small = 1.0e-20L, one = 1.0, two = 2.0, 66 #ifndef lint 67 big = 1.0e+20L, 68 #endif 69 threshold = 45.0L; 70 71 long double 72 tanhl(long double x) { 73 long double t, y, z; 74 int signx; 75 #ifndef lint 76 volatile long double dummy; 77 #endif 78 79 if (isnanl(x)) 80 return (x + x); /* x is NaN */ 81 signx = signbitl(x); 82 t = fabsl(x); 83 z = one; 84 if (t <= threshold) { 85 if (t > one) 86 z = one - two / (expm1l(t + t) + two); 87 else if (t > small) { 88 y = expm1l(-t - t); 89 z = -y / (y + two); 90 } else { 91 #ifndef lint 92 dummy = t + big; 93 /* inexact if t != 0 */ 94 #endif 95 return (x); 96 } 97 } else if (!finitel(t)) 98 return (copysignl(one, x)); 99 else 100 return (signx ? -z + small * small : z - small * small); 101 return (signx ? -z : z); 102 } 103