ndarray.js (2332B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2019 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // VARIABLES // 22 23 var M = 5; 24 25 26 // MAIN // 27 28 /** 29 * Computes the dot product of `x` and `y`. 30 * 31 * @param {integer} N - number of values over which to compute the dot product 32 * @param {Float64Array} x - first input array 33 * @param {integer} strideX - `x` stride length 34 * @param {NonNegativeInteger} offsetX - starting index for `x` 35 * @param {Float64Array} y - second input array 36 * @param {integer} strideY - `y` stride length 37 * @param {NonNegativeInteger} offsetY - starting index for `y` 38 * @returns {number} dot product of `x` and `y` 39 * 40 * @example 41 * var Float64Array = require( '@stdlib/array/float64' ); 42 * 43 * var x = new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ); 44 * var y = new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ); 45 * 46 * var z = ddot( x.length, x, 1, 0, y, 1, 0 ); 47 * // returns -5.0 48 */ 49 function ddot( N, x, strideX, offsetX, y, strideY, offsetY ) { 50 var dot; 51 var ix; 52 var iy; 53 var m; 54 var i; 55 56 dot = 0.0; 57 if ( N <= 0 ) { 58 return dot; 59 } 60 ix = offsetX; 61 iy = offsetY; 62 63 // Use unrolled loops if both strides are equal to `1`... 64 if ( strideX === 1 && strideY === 1 ) { 65 m = N % M; 66 67 // If we have a remainder, run a clean-up loop... 68 if ( m > 0 ) { 69 for ( i = 0; i < m; i++ ) { 70 dot += ( x[ ix ] * y[ iy ] ); 71 ix += 1; 72 iy += 1; 73 } 74 } 75 if ( N < M ) { 76 return dot; 77 } 78 for ( i = m; i < N; i += M ) { 79 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 80 ix += M; 81 iy += M; 82 } 83 return dot; 84 } 85 for ( i = 0; i < N; i++ ) { 86 dot += x[ ix ] * y[ iy ]; 87 ix += strideX; 88 iy += strideY; 89 } 90 return dot; 91 } 92 93 94 // EXPORTS // 95 96 module.exports = ddot;