79 lines
1.9 KiB
JavaScript
79 lines
1.9 KiB
JavaScript
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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var abs = require( '@stdlib/math/base/special/abs' );
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// MAIN //
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/**
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* Expands a strides array to accommodate an expanded array shape (i.e., an array shape with prepended singleton dimensions).
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*
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* @private
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* @param {NonNegativeInteger} ndims - number of dimensions
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* @param {Array} shape - expanded array shape
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* @param {Array} strides - strides array
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* @param {string} order - memory layout order
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* @returns {Array} output strides array
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*
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* @example
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* var out = expandStrides( 4, [ 1, 1, 2, 2 ], [ 1, 2 ], 'column-major' );
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* // returns [ 1, 1, 1, 2 ]
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*
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* @example
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* var out = expandStrides( 4, [ 1, 1, 2, 2 ], [ 2, 1 ], 'row-major' );
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* // returns [ 4, 4, 2, 1 ]
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*/
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function expandStrides( ndims, shape, strides, order ) {
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var out;
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var N;
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var s;
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var i;
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var j;
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N = strides.length;
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j = ndims - N;
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out = [];
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if ( order === 'row-major' ) {
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s = abs( strides[ 0 ] ) * shape[ j ]; // at `j` is the size of the first non-prepended dimension
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for ( i = 0; i < j; i++ ) {
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out.push( s );
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}
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for ( i = 0; i < N; i++ ) {
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out.push( strides[ i ] );
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}
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} else { // column-major
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for ( i = 0; i < j; i++ ) {
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out.push( 1 );
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}
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for ( i = 0; i < N; i++ ) {
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out.push( strides[ i ] );
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}
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}
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return out;
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}
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// EXPORTS //
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module.exports = expandStrides;
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