time-to-botec

Benchmark sampling in different programming languages
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factory.js (4160B)

      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 setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
     24 var isArrayLike = require( '@stdlib/assert/is-array-like' );
     25 var isTypedArrayLike = require( '@stdlib/assert/is-typed-array-like' );
     26 var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
     27 var deepCopy = require( '@stdlib/utils/copy' );
     28 var floor = require( '@stdlib/math/base/special/floor' );
     29 var randu = require( './../../base/mt19937' ).factory;
     30 var defaults = require( './defaults.json' );
     31 var validate = require( './validate.js' );
     32 
     33 
     34 // MAIN //
     35 
     36 /**
     37 * Returns a function to create a random permutation of elements from an array-like object.
     38 *
     39 * @param {Options} [config] - function options
     40 * @param {PositiveInteger} [config.seed] - integer-valued seed
     41 * @param {string} [config.copy="shallow"] - default copy option (`deep`, `shallow` or `none`)
     42 * @throws {TypeError} options argument must be an object
     43 * @returns {Function} shuffle function
     44 *
     45 * @example
     46 * var shuffle = factory({
     47 *     'seed': 249
     48 * });
     49 * var data = [ 3, 8, 4, 8 ];
     50 * var out = shuffle( data );
     51 * // e.g., returns [ 4, 3, 8, 8 ]
     52 */
     53 function factory( config ) {
     54 	var conf;
     55 	var rand;
     56 	var err;
     57 
     58 	conf = deepCopy( defaults );
     59 	if ( arguments.length ) {
     60 		err = validate( conf, config );
     61 		if ( err ) {
     62 			throw err;
     63 		}
     64 	}
     65 	if ( config && config.seed ) {
     66 		rand = randu({
     67 			'seed': config.seed
     68 		});
     69 	} else {
     70 		rand = randu();
     71 	}
     72 	setReadOnly( shuffle, 'seed', rand.seed );
     73 	setReadOnly( shuffle, 'PRNG', rand );
     74 
     75 	rand = rand.normalized;
     76 
     77 	return shuffle;
     78 
     79 	/**
     80 	* Returns a random permutation of elements in `arr`.
     81 	*
     82 	* @private
     83 	* @param {(ArrayLike|TypedArrayLike)} arr - array-like object to shuffle
     84 	* @param {Options} [options] - function options
     85 	* @param {string} [options.copy] - string indicating whether to return a copy (`deep`,`shallow` or `none`)
     86 	* @throws {TypeError} first argument must be array-like
     87 	* @throws {TypeError} `options` must be an object
     88 	* @throws {TypeError} must provide valid options
     89 	* @returns {ArrayLike} the shuffled array-like object
     90 	*
     91 	* @example
     92 	* var data = [ 1, 2, 3 ];
     93 	* var out = shuffle( data );
     94 	* // e.g., returns [ 3, 1, 2 ]
     95 	*
     96 	* @example
     97 	* var data = [ 1, 2, 3 ];
     98 	* var out = shuffle( data, {
     99 	*     'copy': 'none'
    100 	* });
    101 	* var bool = ( data === out );
    102 	* // returns true
    103 	*/
    104 	function shuffle( arr, options ) {
    105 		var strflg;
    106 		var level;
    107 		var copy;
    108 		var opts;
    109 		var err;
    110 		var out;
    111 		var tmp;
    112 		var N;
    113 		var i;
    114 		var j;
    115 
    116 		if ( !( isArrayLike( arr ) || isTypedArrayLike( arr ) ) ) {
    117 			throw new TypeError( 'invalid argument. First argument must be array-like. Value: `' + arr + '`.' );
    118 		}
    119 		if ( arguments.length > 1 ) {
    120 			opts = {};
    121 			err = validate( opts, options );
    122 			if ( err ) {
    123 				throw err;
    124 			}
    125 		}
    126 		copy = ( opts && opts.copy ) ? opts.copy : conf.copy;
    127 
    128 		strflg = isString( arr );
    129 		if ( strflg ) {
    130 			arr = arr.split( '' );
    131 			copy = 'none';
    132 		}
    133 
    134 		level = 0;
    135 		if ( copy === 'shallow' ) {
    136 			level += 1;
    137 		} else if ( copy === 'deep' ) {
    138 			level += 2;
    139 		}
    140 		N = arr.length;
    141 		out = deepCopy( arr, level );
    142 
    143 		// Note: we skip the first element, as no further swaps are possible given that all other indices are excluded from swapping...
    144 		for ( i = N - 1; i > 0; i-- ) {
    145 			// Generate an integer index on the interval [0,i]:
    146 			j = floor( rand() * (i+1.0) );
    147 
    148 			// Swap elements:
    149 			tmp = out[ i ];
    150 			out[ i ] = out[ j ];
    151 			out[ j ] = tmp;
    152 		}
    153 
    154 		if ( strflg ) {
    155 			out = arr.join( '' );
    156 		}
    157 		return out;
    158 	}
    159 }
    160 
    161 
    162 // EXPORTS //
    163 
    164 module.exports = factory;