99 lines
2.2 KiB
JavaScript
99 lines
2.2 KiB
JavaScript
/**
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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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// FUNCTIONS //
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/**
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* Generates a stride array from an array shape (row-major).
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*
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* @private
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* @param {NonNegativeIntegerArray} shape - array shape
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* @param {(Array|TypedArray|Object)} out - output object
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* @returns {(Array|TypedArray|Object)} array strides
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*/
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function rowmajor( shape, out ) {
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var ndims;
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var s;
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var i;
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ndims = shape.length;
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s = 1;
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for ( i = ndims-1; i >= 0; i-- ) {
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out[ i ] = s;
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s *= shape[ i ];
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}
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return out;
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}
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/**
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* Generates a stride array from an array shape (column-major).
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*
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* @private
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* @param {NonNegativeIntegerArray} shape - array shape
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* @param {(Array|TypedArray|Object)} out - output object
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* @returns {(Array|TypedArray|Object)} array strides
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*/
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function columnmajor( shape, out ) {
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var s;
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var i;
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s = 1;
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for ( i = 0; i < shape.length; i++ ) {
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out[ i ] = s;
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s *= shape[ i ];
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}
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return out;
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}
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// MAIN //
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/**
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* Generates a stride array from an array shape.
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*
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* @param {NonNegativeIntegerArray} shape - array shape
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* @param {string} order - specifies whether an array is row-major (C-style) or column-major (Fortran-style)
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* @param {(Array|TypedArray|Object)} out - output object
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* @returns {(Array|TypedArray|Object)} array strides
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*
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* @example
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* var strides = [ 0, 0 ];
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*
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* var out = shape2strides( [ 3, 2 ], 'row-major', strides );
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* // returns [ 2, 1 ]
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*
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* var bool = ( out === strides );
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* // returns true
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*
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* out = shape2strides( [ 3, 2 ], 'column-major', strides );
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* // returns [ 1, 3 ]
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*/
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function shape2strides( shape, order, out ) {
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if ( order === 'column-major' ) {
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return columnmajor( shape, out );
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}
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return rowmajor( shape, out );
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}
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// EXPORTS //
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module.exports = shape2strides;
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