https://github.com/stdlib-js/blas-ddot
Calculate the dot product of two double-precision floating-point vectors.
https://github.com/stdlib-js/blas-ddot
algebra blas ddot dot dot-product inner inner-product javascript level-1 linear math mathematics node node-js nodejs product scalar scalar-product stdlib subroutines
Last synced: 5 months ago
JSON representation
Calculate the dot product of two double-precision floating-point vectors.
- Host: GitHub
- URL: https://github.com/stdlib-js/blas-ddot
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-15T19:00:22.000Z (almost 5 years ago)
- Default Branch: main
- Last Pushed: 2025-12-29T00:46:35.000Z (6 months ago)
- Last Synced: 2025-12-31T18:49:15.961Z (5 months ago)
- Topics: algebra, blas, ddot, dot, dot-product, inner, inner-product, javascript, level-1, linear, math, mathematics, node, node-js, nodejs, product, scalar, scalar-product, stdlib, subroutines
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 6.45 MB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
- Notice: NOTICE
Awesome Lists containing this project
README
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# ddot
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Calculate the dot product of two double-precision floating-point vectors.
The [dot product][dot-product] (or scalar product) is defined as
```math
\mathbf{x}\cdot\mathbf{y} = \sum_{i=0}^{N-1} x_i y_i = x_0 y_0 + x_1 y_1 + \ldots + x_{N-1} y_{N-1}
```
## Installation
```bash
npm install @stdlib/blas-ddot
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var ddot = require( '@stdlib/blas-ddot' );
```
#### ddot( x, y\[, dim] )
Calculates the dot product of two double-precision floating-point vectors `x` and `y`.
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );
var z = ddot( x, y );
// returns
var v = z.get();
// returns -5.0
```
The function has the following parameters:
- **x**: a non-zero-dimensional [`ndarray`][@stdlib/ndarray/ctor] whose underlying data type is `float64`. Must be [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with `y`.
- **y**: a non-zero-dimensional [`ndarray`][@stdlib/ndarray/ctor] whose underlying data type is `float64`. Must be [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with `x`.
- **dim**: dimension for which to compute the dot product. Must be a negative integer. Negative indices are resolved relative to the last array dimension, with the last dimension corresponding to `-1`. Default: `-1`.
If provided at least one input [`ndarray`][@stdlib/ndarray/ctor] having more than one dimension, the input [`ndarrays`][@stdlib/ndarray/ctor] are [broadcasted][@stdlib/ndarray/base/broadcast-shapes] to a common shape. For multi-dimensional input [`ndarrays`][@stdlib/ndarray/ctor], the function performs batched computation, such that the function computes the dot product for each pair of vectors in `x` and `y` according to the specified dimension index.
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var array = require( '@stdlib/ndarray-array' );
var opts = {
'shape': [ 2, 3 ]
};
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0, 3.0 ] ), opts );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0, 2.0 ] ), opts );
var z = ddot( x, y );
// returns
var v1 = z.get( 0 );
// returns 23.0
var v2 = z.get( 1 );
// returns -22.0
```
## Notes
- The size of the contracted dimension must be the same for both input [`ndarrays`][@stdlib/ndarray/ctor].
- The function resolves the dimension index for which to compute the dot product **before** broadcasting.
- Negative indices are resolved relative to the last [`ndarray`][@stdlib/ndarray/ctor] dimension, with the last dimension corresponding to `-1`.
- The output [`ndarray`][@stdlib/ndarray/ctor] has the same data type as the input [`ndarrays`][@stdlib/ndarray/ctor] and has a shape which is determined by broadcasting and excludes the contracted dimension.
- If provided empty vectors, the dot product is `0`.
- `ddot()` provides a higher-level interface to the [BLAS][blas] level 1 function [`ddot`][@stdlib/blas/base/ddot].
## Examples
```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );
var ddot = require( '@stdlib/blas-ddot' );
var opts = {
'dtype': 'float64'
};
var x = array( discreteUniform( 10, 0, 100, opts ), {
'shape': [ 5, 2 ]
});
console.log( ndarray2array( x ) );
var y = array( discreteUniform( 10, 0, 10, opts ), {
'shape': x.shape
});
console.log( ndarray2array( y ) );
var z = ddot( x, y, -1 );
console.log( ndarray2array( z ) );
```
* * *
## See Also
- [`@stdlib/blas-base/ddot`][@stdlib/blas/base/ddot]: calculate the dot product of two double-precision floating-point vectors.
- [`@stdlib/blas-gdot`][@stdlib/blas/gdot]: calculate the dot product of two vectors.
- [`@stdlib/blas-sdot`][@stdlib/blas/sdot]: calculate the dot product of two single-precision floating-point vectors.
* * *
## 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 © 2016-2025. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-ddot.svg
[npm-url]: https://npmjs.org/package/@stdlib/blas-ddot
[test-image]: https://github.com/stdlib-js/blas-ddot/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/blas-ddot/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-ddot/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/blas-ddot?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-ddot/tree/deno
[deno-readme]: https://github.com/stdlib-js/blas-ddot/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/blas-ddot/tree/umd
[umd-readme]: https://github.com/stdlib-js/blas-ddot/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/blas-ddot/tree/esm
[esm-readme]: https://github.com/stdlib-js/blas-ddot/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/blas-ddot/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ddot/main/LICENSE
[dot-product]: https://en.wikipedia.org/wiki/Dot_product
[blas]: http://www.netlib.org/blas
[@stdlib/ndarray/ctor]: https://github.com/stdlib-js/ndarray-ctor
[@stdlib/ndarray/base/broadcast-shapes]: https://github.com/stdlib-js/ndarray-base-broadcast-shapes
[@stdlib/blas/base/ddot]: https://github.com/stdlib-js/blas-base-ddot
[@stdlib/blas/gdot]: https://github.com/stdlib-js/blas-gdot
[@stdlib/blas/sdot]: https://github.com/stdlib-js/blas-sdot