gapxsumors.js (1462B)
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 // MAIN // 22 23 /** 24 * Adds a constant to each strided array element and computes the sum using ordinary recursive summation. 25 * 26 * @param {PositiveInteger} N - number of indexed elements 27 * @param {number} alpha - constant 28 * @param {NumericArray} x - input array 29 * @param {integer} stride - stride length 30 * @returns {number} sum 31 * 32 * @example 33 * var x = [ 1.0, -2.0, 2.0 ]; 34 * var N = x.length; 35 * 36 * var v = gapxsumors( N, 5.0, x, 1 ); 37 * // returns 16.0 38 */ 39 function gapxsumors( N, alpha, x, stride ) { 40 var sum; 41 var ix; 42 var i; 43 44 if ( N <= 0 ) { 45 return 0.0; 46 } 47 if ( N === 1 || stride === 0 ) { 48 return alpha + x[ 0 ]; 49 } 50 if ( stride < 0 ) { 51 ix = (1-N) * stride; 52 } else { 53 ix = 0; 54 } 55 sum = 0.0; 56 for ( i = 0; i < N; i++ ) { 57 sum += alpha + x[ ix ]; 58 ix += stride; 59 } 60 return sum; 61 } 62 63 64 // EXPORTS // 65 66 module.exports = gapxsumors;