time-to-botec

factory.js (7257B)

---

 /**
 * @license Apache-2.0
 *
 * Copyright (c) 2018 The Stdlib Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
 'use strict';
 
 // MODULES //
 
 var setReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
 var setReadOnlyAccessor = require( '@stdlib/utils/define-nonenumerable-read-only-accessor' );
 var setReadWriteAccessor = require( '@stdlib/utils/define-nonenumerable-read-write-accessor' );
 var isFunction = require( '@stdlib/assert/is-function' );
 var isObject = require( '@stdlib/assert/is-plain-object' );
 var isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
 var isUint32Array = require( '@stdlib/assert/is-uint32array' );
 var mt19937 = require( './../../../base/mt19937' ).factory;
 var constantFunction = require( '@stdlib/utils/constant-function' );
 var noop = require( '@stdlib/utils/noop' );
 var floor = require( '@stdlib/math/base/special/floor' );
 var UINT32_MAX = require( '@stdlib/constants/uint32/max' );
 var typedarray2json = require( '@stdlib/array/to-json' );
 var improvedZiggurat = require( './improved_ziggurat.js' );
 
 
 // MAIN //
 
 /**
 * Returns a pseudorandom number generator which implements the improved Ziggurat method to generate normally distributed pseudorandom numbers.
 *
 * @param {Options} [options] - function options
 * @param {PRNG} [options.prng] - pseudorandom number generator which generates uniformly distributed pseudorandom numbers
 * @param {PRNGSeedMT19937} [options.seed] - pseudorandom number generator seed
 * @param {PRNGStateMT19937} [options.state] - pseudorandom number generator state
 * @param {boolean} [options.copy=true] - boolean indicating whether to copy a provided pseudorandom number generator state
 * @throws {TypeError} must provide an object
 * @throws {TypeError} must provide valid options
 * @throws {Error} must provide a valid state
 * @returns {PRNG} pseudorandom number generator
 *
 * @example
 * var randn = factory();
 *
 * var r = randn();
 * // returns <number>
 *
 * @example
 * // Return a seeded PRNG:
 * var randn = factory({
 *     'seed': 12345
 * });
 *
 * var r = randn();
 * // returns <number>
 */
 function factory( options ) {
 	var randu;
 	var randi;
 	var randn;
 	var opts;
 
 	opts = {
 		'copy': true
 	};
 	if ( arguments.length ) {
 		if ( !isObject( options ) ) {
 			throw new TypeError( 'invalid argument. Must provide an object. Value: `' + options + '`.' );
 		}
 		if ( hasOwnProp( options, 'copy' ) ) {
 			opts.copy = options.copy;
 			if ( !isBoolean( options.copy ) ) {
 				throw new TypeError( 'invalid option. `copy` option must be a boolean. Option: `' + options.copy + '`.' );
 			}
 		}
 		if ( hasOwnProp( options, 'prng' ) ) {
 			if ( !isFunction( options.prng ) ) {
 				throw new TypeError( 'invalid option. `prng` option must be a pseudorandom number generator function. Option: `' + options.prng + '`.' );
 			}
 			randu = options.prng;
 		}
 		// If provided a PRNG, ignore the `state` option, as we don't support getting or setting PRNG state.
 		else if ( hasOwnProp( options, 'state' ) ) {
 			opts.state = options.state;
 			if ( !isUint32Array( options.state ) ) {
 				throw new TypeError( 'invalid option. `state` option must be a Uint32Array. Option: `' + options.state + '`.' );
 			}
 		}
 		// If provided a PRNG, ignore the `seed` option, as a `seed`, by itself, is insufficient to guarantee reproducibility. If provided a state, ignore the `seed` option, as a PRNG state should contain seed information.
 		else if ( hasOwnProp( options, 'seed' ) ) {
 			opts.seed = options.seed;
 			if ( options.seed === void 0 ) {
 				throw new TypeError( 'invalid option. `seed` option must be either a positive integer less than or equal to the maximum unsigned 32-bit integer or an array-like object containing integer values less than or equal to the maximum unsigned 32-bit integer. Option: `' + options.seed + '`.' );
 			}
 		}
 	}
 	if ( opts.state === void 0 ) {
 		if ( randu === void 0 ) {
 			randi = mt19937( opts );
 			randu = randi.normalized;
 		} else {
 			randi = mt19937({
 				'seed': floor( 1.0 + ( UINT32_MAX*randu() ) ), // allows seeding via an externally seeded PRNG
 				'copy': opts.copy
 			});
 			opts.seed = null;
 		}
 	} else {
 		randi = mt19937( opts );
 		randu = randi.normalized;
 	}
 	randn = improvedZiggurat( randu, randi );
 
 	setReadOnly( randn, 'NAME', 'improved-ziggurat' );
 	if ( opts.seed === null ) {
 		setReadOnly( randn, 'seed', null );
 		setReadOnly( randn, 'seedLength', null );
 	} else {
 		setReadOnlyAccessor( randn, 'seed', getSeed );
 		setReadOnlyAccessor( randn, 'seedLength', getSeedLength );
 	}
 	// If we are provided an "external" PRNG, we don't support getting or setting PRNG state, as we'd need to check for compatible state value types, etc, entailing considerable complexity.
 	if ( options && options.prng ) {
 		setReadWriteAccessor( randn, 'state', constantFunction( null ), noop );
 		setReadOnly( randn, 'stateLength', null );
 		setReadOnly( randn, 'byteLength', null );
 		setReadOnly( randn, 'toJSON', constantFunction( null ) );
 	} else {
 		setReadWriteAccessor( randn, 'state', getState, setState );
 		setReadOnlyAccessor( randn, 'stateLength', getStateLength );
 		setReadOnlyAccessor( randn, 'byteLength', getStateSize );
 		setReadOnly( randn, 'toJSON', toJSON );
 	}
 	setReadOnly( randn, 'PRNG', randu );
 
 	return randn;
 
 	/**
 	* Returns the PRNG seed.
 	*
 	* @private
 	* @returns {PRNGSeedMT19937} seed
 	*/
 	function getSeed() {
 		return randi.seed;
 	}
 
 	/**
 	* Returns the PRNG seed length.
 	*
 	* @private
 	* @returns {PositiveInteger} seed length
 	*/
 	function getSeedLength() {
 		return randi.seedLength;
 	}
 
 	/**
 	* Returns the PRNG state length.
 	*
 	* @private
 	* @returns {PositiveInteger} state length
 	*/
 	function getStateLength() {
 		return randi.stateLength;
 	}
 
 	/**
 	* Returns the PRNG state size (in bytes).
 	*
 	* @private
 	* @returns {PositiveInteger} state size (in bytes)
 	*/
 	function getStateSize() {
 		return randi.byteLength;
 	}
 
 	/**
 	* Returns the current PRNG state.
 	*
 	* @private
 	* @returns {PRNGStateMT19937} current state
 	*/
 	function getState() {
 		return randi.state;
 	}
 
 	/**
 	* Sets the PRNG state.
 	*
 	* @private
 	* @param {PRNGStateMT19937} s - generator state
 	* @throws {Error} must provide a valid state
 	*/
 	function setState( s ) {
 		randi.state = s;
 	}
 
 	/**
 	* Serializes the pseudorandom number generator as a JSON object.
 	*
 	* ## Notes
 	*
 	* -   `JSON.stringify()` implicitly calls this method when stringifying a PRNG.
 	*
 	* @private
 	* @returns {Object} JSON representation
 	*/
 	function toJSON() {
 		var out = {};
 		out.type = 'PRNG';
 		out.name = randn.NAME;
 		out.state = typedarray2json( randi.state );
 		out.params = [];
 		return out;
 	}
 }
 
 
 // EXPORTS //
 
 module.exports = factory;