ndarray.js (1914B)
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 = 6; 24 25 26 // MAIN // 27 28 /** 29 * Computes the sum of strided array elements using ordinary recursive summation. 30 * 31 * @param {PositiveInteger} N - number of indexed elements 32 * @param {NumericArray} x - input array 33 * @param {integer} stride - stride length 34 * @param {NonNegativeInteger} offset - starting index 35 * @returns {number} sum 36 * 37 * @example 38 * var floor = require( '@stdlib/math/base/special/floor' ); 39 * 40 * var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ]; 41 * var N = floor( x.length / 2 ); 42 * 43 * var v = gsumors( N, x, 2, 1 ); 44 * // returns 5.0 45 */ 46 function gsumors( N, x, stride, offset ) { 47 var ix; 48 var m; 49 var s; 50 var i; 51 52 s = 0.0; 53 if ( N <= 0 ) { 54 return s; 55 } 56 if ( N === 1 || stride === 0 ) { 57 return x[ offset ]; 58 } 59 ix = offset; 60 61 // If the stride is equal to `1`, use unrolled loops... 62 if ( stride === 1 ) { 63 m = N % M; 64 65 // If we have a remainder, run a clean-up loop... 66 if ( m > 0 ) { 67 for ( i = 0; i < m; i++ ) { 68 s += x[ ix ]; 69 ix += stride; 70 } 71 } 72 if ( N < M ) { 73 return s; 74 } 75 for ( i = m; i < N; i += M ) { 76 s += x[ix] + x[ix+1] + x[ix+2] + x[ix+3] + x[ix+4] + x[ix+5]; 77 ix += M; 78 } 79 return s; 80 } 81 for ( i = 0; i < N; i++ ) { 82 s += x[ ix ]; 83 ix += stride; 84 } 85 return s; 86 } 87 88 89 // EXPORTS // 90 91 module.exports = gsumors;