time-to-botec

main.js (4754B)

---

 /**
 * @license Apache-2.0
 *
 * Copyright (c) 2021 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';
 
 // MAIN //
 
 /**
 * Broadcasts array shapes to a single shape.
 *
 * ## Notes
 *
 * -   Two respective dimensions in two shape arrays are compatible if
 *
 *     1.  the dimensions are equal.
 *     2.  one dimension is `1`.
 *
 * -   The function returns `null` if provided incompatible shapes (i.e., shapes which cannot be broadcast with one another).
 *
 * @param {Array<NonNegativeIntegerArray>} shapes - array of shape arrays
 * @returns {(NonNegativeIntegerArray|null)} broadcast shape (or `null`)
 *
 * @example
 * var shapes = [
 *     [ 8, 1, 6, 1 ],
 *     [ 7, 1, 5 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 8, 7, 6, 5 ]
 *
 * @example
 * var shapes = [
 *     [ 5, 4 ],
 *     [ 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 5, 4 ]
 *
 * @example
 * var shapes = [
 *     [ 5, 4 ],
 *     [ 4 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 5, 4 ]
 *
 * @example
 * var shapes = [
 *     [ 15, 3, 5 ],
 *     [ 15, 1, 5 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 15, 3, 5 ]
 *
 * @example
 * var shapes = [
 *     [ 15, 3, 5 ],
 *     [ 3, 5 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 15, 3, 5 ]
 *
 * @example
 * var shapes = [
 *     [ 15, 3, 5 ],
 *     [ 3, 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 15, 3, 5 ]
 *
 * @example
 * var shapes = [
 *     [ 8, 1, 1, 6, 1 ],
 *     [ 1, 7, 1, 5 ],
 *     [ 8, 4, 1, 6, 5 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 8, 4, 7, 6, 5 ]
 *
 * @example
 * var shapes = [
 *     [ 8, 1, 1, 6, 1 ],
 *     [ 0 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 8, 1, 1, 6, 0 ]
 *
 * @example
 * var shapes = [
 *     [ 8, 1, 1, 6, 1 ],
 *     [ 8, 0, 1, 6, 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 8, 0, 1, 6, 1 ]
 *
 * @example
 * var shapes = [
 *     [ 8, 8, 1, 6, 1 ],
 *     [ 8, 0, 1, 6, 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns null
 *
 * @example
 * var shapes = [
 *     [ 8, 0, 1, 6, 1 ],
 *     [ 8, 8, 1, 6, 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns null
 *
 * @example
 * var shapes = [
 *     []
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns []
 *
 * @example
 * var shapes = [
 *     [],
 *     []
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns []
 *
 * @example
 * var shapes = [];
 *
 * var out = broadcastShapes( shapes );
 * // returns []
 *
 * @example
 * var shapes = [
 *     [ 3, 2, 1 ],
 *     []
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 3, 2, 1 ]
 *
 * @example
 * var shapes = [
 *     [],
 *     [ 3, 2, 1 ]
 * ];
 *
 * var out = broadcastShapes( shapes );
 * // returns [ 3, 2, 1 ]
 */
 function broadcastShapes( shapes ) {
 	var ndims;
 	var out;
 	var dim;
 	var sh;
 	var n1;
 	var n2;
 	var d;
 	var M;
 	var N;
 	var i;
 	var j;
 
 	M = shapes.length;
 	out = [];
 	if ( M === 0 ) {
 		return out;
 	}
 	sh = shapes[ 0 ];
 	N = sh.length;
 
 	// If provided a single input shape array, then the broadcast shape is input shape...
 	if ( M === 1 ) {
 		// Need to manually copy to output shape, as shapes could be array-like objects...
 		for ( i = 0; i < N; i++ ) {
 			out.push( sh[ i ] );
 		}
 		return out;
 	}
 	// Determine the maximum dimensionality...
 	ndims = [ N ];
 	for ( i = 1; i < M; i++ ) {
 		ndims.push( shapes[ i ].length );
 		if ( ndims[ i ] > N ) {
 			N = ndims[ i ];
 		}
 	}
 	// Initialize the output array...
 	for ( i = 0; i < N; i++ ) {
 		out.push( 0 );
 	}
 	// Compute the broadcast shape...
 	i = N - 1;
 	while ( i >= 0 ) {
 		n1 = ndims[ 0 ] - N + i;
 		if ( n1 >= 0 ) {
 			dim = sh[ n1 ];
 		} else {
 			dim = 1;
 		}
 		for ( j = 1; j < M; j++ ) {
 			n2 = ndims[ j ] - N + i;
 			if ( n2 >= 0 ) {
 				d = shapes[ j ][ n2 ];
 			} else {
 				d = 1;
 			}
 			if ( dim === 1 ) {
 				dim = d;
 				continue;
 			}
 			if ( d === 1 || dim === d ) {
 				// When either `d` is `1` or `d` equals the current output shape dimension, the current output shape dimension remains the same...
 				continue;
 			}
 			// The current shape cannot be broadcast against one of the other shapes...
 			return null;
 		}
 		out[ i ] = dim;
 		i -= 1;
 	}
 	return out;
 }
 
 
 // EXPORTS //
 
 module.exports = broadcastShapes;