dapxsumors.js (1573B)
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 double-precision floating-point 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 {Float64Array} x - input array 29 * @param {integer} stride - stride length 30 * @returns {number} sum 31 * 32 * @example 33 * var Float64Array = require( '@stdlib/array/float64' ); 34 * 35 * var x = new Float64Array( [ 1.0, -2.0, 2.0 ] ); 36 * var N = x.length; 37 * 38 * var v = dapxsumors( N, 5.0, x, 1 ); 39 * // returns 16.0 40 */ 41 function dapxsumors( N, alpha, x, stride ) { 42 var sum; 43 var ix; 44 var i; 45 46 if ( N <= 0 ) { 47 return 0.0; 48 } 49 if ( N === 1 || stride === 0 ) { 50 return alpha + x[ 0 ]; 51 } 52 if ( stride < 0 ) { 53 ix = (1-N) * stride; 54 } else { 55 ix = 0; 56 } 57 sum = 0.0; 58 for ( i = 0; i < N; i++ ) { 59 sum += alpha + x[ ix ]; 60 ix += stride; 61 } 62 return sum; 63 } 64 65 66 // EXPORTS // 67 68 module.exports = dapxsumors;