98 lines
2.2 KiB
JavaScript
98 lines
2.2 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2019 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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// VARIABLES //
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var M = 5;
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// MAIN //
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/**
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* Computes the dot product of `x` and `y`.
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*
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* @param {PositiveInteger} N - number of values over which to compute the dot product
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* @param {Float64Array} x - first input array
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* @param {integer} strideX - `x` stride length
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* @param {Float64Array} y - second input array
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* @param {integer} strideY - `y` stride length
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* @returns {number} dot product of `x` and `y`
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*
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* @example
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* var Float64Array = require( '@stdlib/array/float64' );
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*
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* var x = new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] );
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* var y = new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] );
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*
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* var z = ddot( x.length, x, 1, y, 1 );
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* // returns -5.0
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*/
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function ddot( N, x, strideX, y, strideY ) {
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var dot;
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var ix;
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var iy;
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var m;
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var i;
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dot = 0.0;
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if ( N <= 0 ) {
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return dot;
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}
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// Use unrolled loops if both strides are equal to `1`...
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if ( strideX === 1 && strideY === 1 ) {
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m = N % M;
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// If we have a remainder, run a clean-up loop...
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if ( m > 0 ) {
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for ( i = 0; i < m; i++ ) {
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dot += x[ i ] * y[ i ];
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}
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}
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if ( N < M ) {
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return dot;
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}
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for ( i = m; i < N; i += M ) {
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dot += ( x[ i ] * y[ i ] ) + ( x[ i+1 ] * y[ i+1 ] ) + ( x[ i+2 ] * y[ i+2 ] ) + ( x[ i+3 ] * y[ i+3 ] ) + ( x[ i+4 ] * y[ i+4 ] ); // eslint-disable-line max-len
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}
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return dot;
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}
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if ( strideX < 0 ) {
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ix = ( 1-N ) * strideX;
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} else {
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ix = 0;
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}
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if ( strideY < 0 ) {
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iy = ( 1-N ) * strideY;
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} else {
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iy = 0;
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}
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for ( i = 0; i < N; i++ ) {
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dot += ( x[ ix ] * y[ iy ] );
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ix += strideX;
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iy += strideY;
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}
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return dot;
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}
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// EXPORTS //
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module.exports = ddot;
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