time-to-botec

Benchmark sampling in different programming languages
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cosh.js (2425B)

      1 /**
      2 * @license Apache-2.0
      3 *
      4 * Copyright (c) 2018 The Stdlib Authors.
      5 *
      6 * Licensed under the Apache License, Version 2.0 (the "License");
      7 * you may not use this file except in compliance with the License.
      8 * You may obtain a copy of the License at
      9 *
     10 *    http://www.apache.org/licenses/LICENSE-2.0
     11 *
     12 * Unless required by applicable law or agreed to in writing, software
     13 * distributed under the License is distributed on an "AS IS" BASIS,
     14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15 * See the License for the specific language governing permissions and
     16 * limitations under the License.
     17 *
     18 *
     19 * ## Notice
     20 *
     21 * The original C code, long comment, copyright, license, and constants are from [Cephes]{@link http://www.netlib.org/cephes}. The implementation follows the original, but has been modified for JavaScript.
     22 *
     23 * ```text
     24 * Copyright 1985, 1995, 2000 by Stephen L. Moshier
     25 *
     26 * Some software in this archive may be from the book _Methods and Programs for Mathematical Functions_ (Prentice-Hall or Simon & Schuster International, 1989) or from the Cephes Mathematical Library, a commercial product. In either event, it is copyrighted by the author. What you see here may be used freely but it comes with no support or guarantee.
     27 *
     28 * Stephen L. Moshier
     29 * moshier@na-net.ornl.gov
     30 * ```
     31 */
     32 
     33 'use strict';
     34 
     35 // MODULES //
     36 
     37 var isnan = require( './../../../../base/assert/is-nan' );
     38 var exp = require( './../../../../base/special/exp' );
     39 
     40 
     41 // MAIN //
     42 
     43 /**
     44 * Computes the hyperbolic cosine of a number.
     45 *
     46 * ## Method
     47 *
     48 * ```tex
     49 * \operatorname{cosh}(x) = \frac{ \exp(x) + \exp(-x) }{2}
     50 * ```
     51 *
     52 * ## Notes
     53 *
     54 * -   Relative error:
     55 *
     56 *     | arithmetic | domain   | # trials | peak    | rms     |
     57 *     |:----------:|:--------:|:--------:|:-------:|:-------:|
     58 *     | DEC        | +- 88    | 50000    | 4.0e-17 | 7.7e-18 |
     59 *     | IEEE       | +-MAXLOG | 30000    | 2.6e-16 | 5.7e-17 |
     60 *
     61 *
     62 * @param {number} x - input value (in radians)
     63 * @returns {number} hyperbolic cosine
     64 *
     65 * @example
     66 * var v = cosh( 0.0 );
     67 * // returns 1.0
     68 *
     69 * @example
     70 * var v = cosh( 2.0 );
     71 * // returns ~3.762
     72 *
     73 * @example
     74 * var v = cosh( -2.0 );
     75 * // returns ~3.762
     76 *
     77 * @example
     78 * var v = cosh( NaN );
     79 * // returns NaN
     80 */
     81 function cosh( x ) {
     82 	if ( isnan( x ) ) {
     83 		return x;
     84 	}
     85 	if ( x < 0.0 ) {
     86 		x = -x;
     87 	}
     88 	if ( x > 21.0 ) {
     89 		return exp( x ) / 2.0;
     90 	}
     91 	return ( exp(x) + exp(-x) ) / 2.0;
     92 }
     93 
     94 
     95 // EXPORTS //
     96 
     97 module.exports = cosh;