ndarray.js (1833B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2020 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 * Multiplies `x` by a scalar `alpha`. 30 * 31 * @param {PositiveInteger} N - number of indexed elements 32 * @param {number} alpha - scalar 33 * @param {NumericArray} x - input array 34 * @param {integer} stride - index increment 35 * @param {NonNegativeInteger} offset - starting index 36 * @returns {NumericArray} input array 37 * 38 * @example 39 * var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ]; 40 * 41 * gscal( 3, 5.0, x, 1, x.length-3 ); 42 * // x => [ 1.0, -2.0, 3.0, -20.0, 25.0, -30.0 ] 43 */ 44 function gscal( N, alpha, x, stride, offset ) { 45 var ix; 46 var m; 47 var i; 48 49 if ( N <= 0 || alpha === 1.0 ) { 50 return x; 51 } 52 ix = offset; 53 54 // Use loop unrolling if the stride is equal to `1`... 55 if ( stride === 1 ) { 56 m = N % M; 57 58 // If we have a remainder, run a clean-up loop... 59 if ( m > 0 ) { 60 for ( i = 0; i < m; i++ ) { 61 x[ ix ] *= alpha; 62 ix += stride; 63 } 64 } 65 if ( N < M ) { 66 return x; 67 } 68 for ( i = m; i < N; i += M ) { 69 x[ i ] *= alpha; 70 x[ i+1 ] *= alpha; 71 x[ i+2 ] *= alpha; 72 x[ i+3 ] *= alpha; 73 x[ i+4 ] *= alpha; 74 } 75 return x; 76 } 77 for ( i = 0; i < N; i++ ) { 78 x[ ix ] *= alpha; 79 ix += stride; 80 } 81 return x; 82 } 83 84 85 // EXPORTS // 86 87 module.exports = gscal;