ndarray.js (2228B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 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 = 4; 24 25 26 // MAIN // 27 28 /** 29 * Multiplies `x` by a constant and adds the result to `y`. 30 * 31 * @param {PositiveInteger} N - number of elements 32 * @param {number} alpha - scalar 33 * @param {NumericArray} x - input array 34 * @param {integer} strideX - `x` stride length 35 * @param {NonNegativeInteger} offsetX - starting `x` index 36 * @param {NumericArray} y - destination array 37 * @param {integer} strideY - `y` stride length 38 * @param {NonNegativeInteger} offsetY - starting `y` index 39 * @returns {NumericArray} `y` 40 * 41 * @example 42 * var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ]; 43 * var y = [ 1.0, 1.0, 1.0, 1.0, 1.0 ]; 44 * var alpha = 5.0; 45 * 46 * gaxpy( x.length, alpha, x, 1, 0, y, 1, 0 ); 47 * // y => [ 6.0, 11.0, 16.0, 21.0, 26.0 ] 48 */ 49 function gaxpy( N, alpha, x, strideX, offsetX, y, strideY, offsetY ) { 50 var ix; 51 var iy; 52 var m; 53 var i; 54 if ( N <= 0 || alpha === 0.0 ) { 55 return y; 56 } 57 ix = offsetX; 58 iy = offsetY; 59 60 // Use unrolled loops if both strides are equal to `1`... 61 if ( strideX === 1 && strideY === 1 ) { 62 m = N % M; 63 64 // If we have a remainder, run a clean-up loop... 65 if ( m > 0 ) { 66 for ( i = 0; i < m; i++ ) { 67 y[ iy ] += alpha * x[ ix ]; 68 ix += strideX; 69 iy += strideY; 70 } 71 } 72 if ( N < M ) { 73 return y; 74 } 75 for ( i = m; i < N; i += M ) { 76 y[ iy ] += alpha * x[ ix ]; 77 y[ iy+1 ] += alpha * x[ ix+1 ]; 78 y[ iy+2 ] += alpha * x[ ix+2 ]; 79 y[ iy+3 ] += alpha * x[ ix+3 ]; 80 ix += M; 81 iy += M; 82 } 83 return y; 84 } 85 for ( i = 0; i < N; i++ ) { 86 y[ iy ] += alpha * x[ ix ]; 87 ix += strideX; 88 iy += strideY; 89 } 90 return y; 91 } 92 93 94 // EXPORTS // 95 96 module.exports = gaxpy;