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