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# dsumkbn [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] > Calculate the sum of double-precision floating-point strided array elements using an improved Kahan–Babuška algorithm.
## Usage ```javascript import dsumkbn from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-ext-base-dsumkbn@deno/mod.js'; ``` #### dsumkbn( N, x, stride ) Computes the sum of double-precision floating-point strided array elements using an improved Kahan–Babuška algorithm. ```javascript import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@deno/mod.js'; var x = new Float64Array( [ 1.0, -2.0, 2.0 ] ); var N = x.length; var v = dsumkbn( N, x, 1 ); // returns 1.0 ``` The function has the following parameters: - **N**: number of indexed elements. - **x**: input [`Float64Array`][@stdlib/array/float64]. - **stride**: index increment for `x`. 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 in the strided array, ```javascript import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@deno/mod.js'; var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] ); var v = dsumkbn( 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 import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@deno/mod.js'; 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 = dsumkbn( 4, x1, 2 ); // returns 5.0 ``` #### dsumkbn.ndarray( N, x, stride, offset ) Computes the sum of double-precision floating-point strided array elements using an improved Kahan–Babuška algorithm and alternative indexing semantics. ```javascript import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@deno/mod.js'; var x = new Float64Array( [ 1.0, -2.0, 2.0 ] ); var v = dsumkbn.ndarray( 3, x, 1, 0 ); // returns 1.0 ``` The function has the following additional parameters: - **offset**: starting index for `x`. 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 value in the strided array starting from the second value ```javascript import Float64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-float64@deno/mod.js'; var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); var v = dsumkbn.ndarray( 4, x, 2, 1 ); // returns 5.0 ```
## Notes - If `N <= 0`, both functions return `0.0`.
## Examples ```javascript var discreteUniform = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-discrete-uniform' ).factory; import filledarrayBy from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-filled-by@deno/mod.js'; import dsumkbn from 'https://cdn.jsdelivr.net/gh/stdlib-js/blas-ext-base-dsumkbn@deno/mod.js'; var x = filledarrayBy( 10, 'float64', discreteUniform( 0, 100 ) ); console.log( x ); var v = dsumkbn( x.length, x, 1 ); console.log( v ); ```
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## References - Neumaier, Arnold. 1974. "Rounding Error Analysis of Some Methods for Summing Finite Sums." _Zeitschrift Für Angewandte Mathematik Und Mechanik_ 54 (1): 39–51. doi:[10.1002/zamm.19740540106][@neumaier:1974a].
* * * ## See Also - [`@stdlib/blas-ext/base/dnansumkbn`][@stdlib/blas/ext/base/dnansumkbn]: calculate the sum of double-precision floating-point strided array elements, ignoring NaN values and using an improved Kahan–Babuška algorithm. - [`@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/dsumkbn2`][@stdlib/blas/ext/base/dsumkbn2]: calculate the sum of double-precision floating-point strided array elements using a second-order iterative Kahan–Babuška algorithm. - [`@stdlib/blas-ext/base/dsumors`][@stdlib/blas/ext/base/dsumors]: calculate the sum of double-precision floating-point strided array elements using ordinary recursive summation. - [`@stdlib/blas-ext/base/dsumpw`][@stdlib/blas/ext/base/dsumpw]: calculate the sum of double-precision floating-point strided array elements using pairwise summation. - [`@stdlib/blas-ext/base/gsumkbn`][@stdlib/blas/ext/base/gsumkbn]: calculate the sum of strided array elements using an improved Kahan–Babuška algorithm. - [`@stdlib/blas-ext/base/ssumkbn`][@stdlib/blas/ext/base/ssumkbn]: calculate the sum of single-precision floating-point strided array elements using an improved Kahan–Babuška algorithm.
* * * ## Notice This package is part of [stdlib][stdlib], a standard library 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-ext-base-dsumkbn.svg [npm-url]: https://npmjs.org/package/@stdlib/blas-ext-base-dsumkbn [test-image]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/actions/workflows/test.yml/badge.svg?branch=main [test-url]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/actions/workflows/test.yml?query=branch:main [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-ext-base-dsumkbn/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/blas-ext-base-dsumkbn?branch=main [chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg [chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im [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-dsumkbn/tree/deno [deno-readme]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/tree/umd [umd-readme]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/tree/esm [esm-readme]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/blas-ext-base-dsumkbn/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-base-dsumkbn/main/LICENSE [@stdlib/array/float64]: https://github.com/stdlib-js/array-float64/tree/deno [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray [@neumaier:1974a]: https://doi.org/10.1002/zamm.19740540106 [@stdlib/blas/ext/base/dnansumkbn]: https://github.com/stdlib-js/blas-ext-base-dnansumkbn/tree/deno [@stdlib/blas/ext/base/dsum]: https://github.com/stdlib-js/blas-ext-base-dsum/tree/deno [@stdlib/blas/ext/base/dsumkbn2]: https://github.com/stdlib-js/blas-ext-base-dsumkbn2/tree/deno [@stdlib/blas/ext/base/dsumors]: https://github.com/stdlib-js/blas-ext-base-dsumors/tree/deno [@stdlib/blas/ext/base/dsumpw]: https://github.com/stdlib-js/blas-ext-base-dsumpw/tree/deno [@stdlib/blas/ext/base/gsumkbn]: https://github.com/stdlib-js/blas-ext-base-gsumkbn/tree/deno [@stdlib/blas/ext/base/ssumkbn]: https://github.com/stdlib-js/blas-ext-base-ssumkbn/tree/deno