time-to-botec

Benchmark sampling in different programming languages
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log10.js (4111B)

      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 following copyright and license were part of the original implementation available as part of [FreeBSD]{@link https://svnweb.freebsd.org/base/release/9.3.0/lib/msun/src/e_log10.c}. The implementation follows the original, but has been modified for JavaScript.
     22 *
     23 * ```text
     24 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
     25 *
     26 * Developed at SunPro, a Sun Microsystems, Inc. business.
     27 * Permission to use, copy, modify, and distribute this
     28 * software is freely granted, provided that this notice
     29 * is preserved.
     30 * ```
     31 */
     32 
     33 'use strict';
     34 
     35 // MODULES //
     36 
     37 var getHighWord = require( '@stdlib/number/float64/base/get-high-word' );
     38 var setHighWord = require( '@stdlib/number/float64/base/set-high-word' );
     39 var setLowWord = require( '@stdlib/number/float64/base/set-low-word' );
     40 var isnan = require( './../../../../base/assert/is-nan' );
     41 var BIAS = require( '@stdlib/constants/float64/exponent-bias' );
     42 var NINF = require( '@stdlib/constants/float64/ninf' );
     43 var klog = require( './klog.js' );
     44 
     45 
     46 // VARIABLES //
     47 
     48 var TWO54 = 1.80143985094819840000e+16;     // 0x43500000, 0x00000000
     49 var IVLN10HI = 4.34294481878168880939e-01;  // 0x3fdbcb7b, 0x15200000
     50 var IVLN10LO = 2.50829467116452752298e-11;  // 0x3dbb9438, 0xca9aadd5
     51 var LOG10_2HI = 3.01029995663611771306e-01; // 0x3FD34413, 0x509F6000
     52 var LOG10_2LO = 3.69423907715893078616e-13; // 0x3D59FEF3, 0x11F12B36
     53 
     54 // 0x000fffff = 1048575 => 0 00000000000 11111111111111111111
     55 var HIGH_SIGNIFICAND_MASK = 0x000fffff|0; // asm type annotation
     56 
     57 // 0x7ff00000 = 2146435072 => 0 11111111111 00000000000000000000 => biased exponent: 2047 = 1023+1023 => 2^1023
     58 var HIGH_MAX_NORMAL_EXP = 0x7ff00000|0; // asm type annotation
     59 
     60 // 0x00100000 = 1048576 => 0 00000000001 00000000000000000000 => biased exponent: 1 = -1022+1023 => 2^-1022
     61 var HIGH_MIN_NORMAL_EXP = 0x00100000|0; // asm type annotation
     62 
     63 // 0x3ff00000 = 1072693248 => 0 01111111111 00000000000000000000 => biased exponent: 1023 = 0+1023 => 2^0 = 1
     64 var HIGH_BIASED_EXP_0 = 0x3ff00000|0; // asm type annotation
     65 
     66 
     67 // MAIN //
     68 
     69 /**
     70 * Evaluates the common logarithm (base ten).
     71 *
     72 * @param {NonNegativeNumber} x - input value
     73 * @returns {number} function value
     74 *
     75 * @example
     76 * var v = log10( 4.0 );
     77 * // returns ~0.602
     78 *
     79 * @example
     80 * var v = log10( 8.0 );
     81 * // returns ~0.903
     82 *
     83 * @example
     84 * var v = log10( 0.0 );
     85 * // returns -Infinity
     86 *
     87 * @example
     88 * var v = log10( Infinity );
     89 * // returns Infinity
     90 *
     91 * @example
     92 * var v = log10( NaN );
     93 * // returns NaN
     94 *
     95 * @example
     96 * var v = log10( -4.0 );
     97 * // returns NaN
     98 */
     99 function log10( x ) {
    100 	var hi;
    101 	var hx;
    102 	var lo;
    103 	var f;
    104 	var i;
    105 	var k;
    106 	var y;
    107 	var z;
    108 
    109 	if ( isnan( x ) || x < 0.0 ) {
    110 		return NaN;
    111 	}
    112 	if ( x === 0.0 ) {
    113 		return NINF;
    114 	}
    115 	hx = getHighWord( x );
    116 	k = 0|0; // asm type annotation
    117 
    118 	// Case: 0 < x < 2**-1022
    119 	if ( hx < HIGH_MIN_NORMAL_EXP ) {
    120 		// Subnormal number, scale up `x`...
    121 		k -= 54|0; // asm type annotation
    122 		x *= TWO54;
    123 		hx = getHighWord( x );
    124 	}
    125 	if ( hx >= HIGH_MAX_NORMAL_EXP ) {
    126 		return x + x;
    127 	}
    128 	k += ((hx>>20) - BIAS)|0; // asm type annotation
    129 	hx &= HIGH_SIGNIFICAND_MASK;
    130 	i = ( (hx+0x95f64)&0x100000 )|0; // asm type annotation
    131 
    132 	// Normalize `x` or `x/2`...
    133 	x = setHighWord( x, hx|(i^HIGH_BIASED_EXP_0) );
    134 	k += (i>>20)|0; // asm type annotation
    135 	y = k;
    136 	f = klog( x );
    137 	x -= 1;
    138 	hi = setLowWord( x, 0.0 );
    139 	lo = x - hi;
    140 	z = (y*LOG10_2LO) + ( (x+f)*IVLN10LO );
    141 	z += ( (lo+f)*IVLN10HI ) + ( hi*IVLN10HI );
    142 	return z + ( y*LOG10_2HI );
    143 }
    144 
    145 
    146 // EXPORTS //
    147 
    148 module.exports = log10;