time-to-botec

Benchmark sampling in different programming languages
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abs.js (2753B)

      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 'use strict';
     20 
     21 // MODULES //
     22 
     23 var Float64Array = require( '@stdlib/array/float64' );
     24 var Uint32Array = require( '@stdlib/array/uint32' );
     25 var HIGH = require( './high.js' );
     26 
     27 
     28 // VARIABLES //
     29 
     30 var FLOAT64_VIEW = new Float64Array( 1 );
     31 var UINT32_VIEW = new Uint32Array( FLOAT64_VIEW.buffer );
     32 
     33 // 0x7fffffff = 2147483647 => 0 11111111111 11111111111111111111
     34 var ABS_MASK = 0x7fffffff>>>0; // asm type annotation
     35 
     36 
     37 // MAIN //
     38 
     39 /**
     40 * Computes the absolute value of a double-precision floating-point number `x`.
     41 *
     42 * ## Notes
     43 *
     44 * ```text
     45 * float64 (64 bits)
     46 * f := fraction (significand/mantissa) (52 bits)
     47 * e := exponent (11 bits)
     48 * s := sign bit (1 bit)
     49 *
     50 * |-------- -------- -------- -------- -------- -------- -------- --------|
     51 * |                                Float64                                |
     52 * |-------- -------- -------- -------- -------- -------- -------- --------|
     53 * |              Uint32               |               Uint32              |
     54 * |-------- -------- -------- -------- -------- -------- -------- --------|
     55 * ```
     56 *
     57 * If little endian (more significant bits last):
     58 *
     59 * ```text
     60 *                         <-- lower      higher -->
     61 * |   f7       f6       f5       f4       f3       f2    e2 | f1 |s|  e1  |
     62 * ```
     63 *
     64 * If big endian (more significant bits first):
     65 *
     66 * ```text
     67 *                         <-- higher      lower -->
     68 * |s| e1    e2 | f1     f2       f3       f4       f5        f6      f7   |
     69 * ```
     70 *
     71 * In which Uint32 can we find the higher order bits? If little endian, the second; if big endian, the first.
     72 *
     73 *
     74 * ## References
     75 *
     76 * -   [Open Group][1]
     77 *
     78 * [1]: http://pubs.opengroup.org/onlinepubs/9629399/chap14.htm
     79 *
     80 * @param {number} x - input value
     81 * @returns {number} absolute value
     82 *
     83 * @example
     84 * var v = abs( -1.0 );
     85 * // returns 1.0
     86 *
     87 * @example
     88 * var v = abs( 2.0 );
     89 * // returns 2.0
     90 *
     91 * @example
     92 * var v = abs( 0.0 );
     93 * // returns 0.0
     94 *
     95 * @example
     96 * var v = abs( -0.0 );
     97 * // returns 0.0
     98 *
     99 * @example
    100 * var v = abs( NaN );
    101 * // returns NaN
    102 */
    103 function abs( x ) {
    104 	FLOAT64_VIEW[ 0 ] = x;
    105 	UINT32_VIEW[ HIGH ] &= ABS_MASK;
    106 	return FLOAT64_VIEW[ 0 ];
    107 }
    108 
    109 
    110 // EXPORTS //
    111 
    112 module.exports = abs;