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# gsum [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] > Calculate the sum of strided array elements.
## Installation ```bash npm install @stdlib/blas-ext-base-gsum ```
## Usage ```javascript var gsum = require( '@stdlib/blas-ext-base-gsum' ); ``` #### gsum( N, x, strideX ) Computes the sum of strided array elements. ```javascript var x = [ 1.0, -2.0, 2.0 ]; var v = gsum( x.length, x, 1 ); // returns 1.0 ``` The function has the following parameters: - **N**: number of indexed elements. - **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array]. - **strideX**: stride length. The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute the sum of every other element: ```javascript var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ]; var v = gsum( 4, x, 2 ); // returns 5.0 ``` Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. ```javascript var Float64Array = require( '@stdlib/array-float64' ); var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element var v = gsum( 4, x1, 2 ); // returns 5.0 ``` #### gsum.ndarray( N, x, strideX, offsetX ) Computes the sum of strided array elements using alternative indexing semantics. ```javascript var x = [ 1.0, -2.0, 2.0 ]; var v = gsum.ndarray( x.length, x, 1, 0 ); // returns 1.0 ``` The function has the following additional parameters: - **offsetX**: starting index. While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to calculate the sum of every other element starting from the second element: ```javascript var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ]; var v = gsum.ndarray( 4, x, 2, 1 ); // returns 5.0 ```
## Notes - If `N <= 0`, both functions return `0.0`. - Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array-base/accessor`][@stdlib/array/base/accessor]). - Depending on the environment, the typed versions ([`dsum`][@stdlib/blas/ext/base/dsum], [`ssum`][@stdlib/blas/ext/base/ssum], etc.) are likely to be significantly more performant.
## Examples ```javascript var discreteUniform = require( '@stdlib/random-array-discrete-uniform' ); var gsum = require( '@stdlib/blas-ext-base-gsum' ); var x = discreteUniform( 10, -100, 100, { 'dtype': 'float64' }); console.log( x ); var v = gsum( x.length, x, 1 ); console.log( v ); ```
* * * ## See Also - [`@stdlib/blas-ext/base/dsum`][@stdlib/blas/ext/base/dsum]: calculate the sum of double-precision floating-point strided array elements. - [`@stdlib/blas-ext/base/gnansum`][@stdlib/blas/ext/base/gnansum]: calculate the sum of strided array elements, ignoring NaN values. - [`@stdlib/blas-ext/base/ssum`][@stdlib/blas/ext/base/ssum]: calculate the sum of single-precision floating-point strided array elements. - [`@stdlib/stats-strided/mean`][@stdlib/stats/strided/mean]: calculate the arithmetic mean of a strided array.
* * * ## Notice This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more. For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib]. #### Community [![Chat][chat-image]][chat-url] --- ## License See [LICENSE][stdlib-license]. ## Copyright Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-ext-base-gsum.svg [npm-url]: https://npmjs.org/package/@stdlib/blas-ext-base-gsum [test-image]: https://github.com/stdlib-js/blas-ext-base-gsum/actions/workflows/test.yml/badge.svg?branch=v0.3.1 [test-url]: https://github.com/stdlib-js/blas-ext-base-gsum/actions/workflows/test.yml?query=branch:v0.3.1 [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-ext-base-gsum/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/blas-ext-base-gsum?branch=main [chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg [chat-url]: https://stdlib.zulipchat.com [stdlib]: https://github.com/stdlib-js/stdlib [stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors [umd]: https://github.com/umdjs/umd [es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules [deno-url]: https://github.com/stdlib-js/blas-ext-base-gsum/tree/deno [deno-readme]: https://github.com/stdlib-js/blas-ext-base-gsum/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/blas-ext-base-gsum/tree/umd [umd-readme]: https://github.com/stdlib-js/blas-ext-base-gsum/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/blas-ext-base-gsum/tree/esm [esm-readme]: https://github.com/stdlib-js/blas-ext-base-gsum/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/blas-ext-base-gsum/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-base-gsum/main/LICENSE [mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array [@stdlib/array/base/accessor]: https://www.npmjs.com/package/@stdlib/array-base-accessor [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray [@stdlib/blas/ext/base/dsum]: https://www.npmjs.com/package/@stdlib/blas-ext-base-dsum [@stdlib/blas/ext/base/gnansum]: https://www.npmjs.com/package/@stdlib/blas-ext-base-gnansum [@stdlib/blas/ext/base/ssum]: https://www.npmjs.com/package/@stdlib/blas-ext-base-ssum [@stdlib/stats/strided/mean]: https://www.npmjs.com/package/@stdlib/stats-strided-mean