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https://github.com/stdlib-js/blas-base-sscal
Multiply a single-precision floating-point vector by a constant.
https://github.com/stdlib-js/blas-base-sscal
algebra alpha array blas dscal javascript level-1 linear math mathematics ndarray node node-js nodejs scal scale sscal stdlib subroutines vector
Last synced: about 7 hours ago
JSON representation
Multiply a single-precision floating-point vector by a constant.
- Host: GitHub
- URL: https://github.com/stdlib-js/blas-base-sscal
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T16:51:48.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2024-04-27T10:00:49.000Z (7 months ago)
- Last Synced: 2024-05-01T11:59:21.308Z (7 months ago)
- Topics: algebra, alpha, array, blas, dscal, javascript, level-1, linear, math, mathematics, ndarray, node, node-js, nodejs, scal, scale, sscal, stdlib, subroutines, vector
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 505 KB
- Stars: 2
- Watchers: 3
- 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
Awesome Lists containing this project
README
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# sscal
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Multiply a single-precision floating-point vector `x` by a constant `alpha`.
## Installation
```bash
npm install @stdlib/blas-base-sscal
```
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 sscal = require( '@stdlib/blas-base-sscal' );
```
#### sscal( N, alpha, x, stride )
Multiplies a single-precision floating-point vector `x` by a constant `alpha`.
```javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sscal( x.length, 5.0, x, 1 );
// x => [ -10.0, 5.0, 15.0, -25.0, 20.0, 0.0, -5.0, -15.0 ]
```
The function has the following parameters:
- **N**: number of indexed elements.
- **alpha**: scalar constant.
- **x**: input [`Float32Array`][@stdlib/array/float32].
- **stride**: index increment.
The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to multiply every other value by a constant
```javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sscal( 4, 5.0, x, 2 );
// x => [ -10.0, 1.0, 15.0, -5.0, 20.0, 0.0, -5.0, -3.0 ]
```
Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
```javascript
var Float32Array = require( '@stdlib/array-float32' );
// Initial array:
var x0 = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
// Create an offset view:
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
// Scale every other value:
sscal( 3, 5.0, x1, 2 );
// x0 => [ 1.0, -10.0, 3.0, -20.0, 5.0, -30.0 ]
```
If either `N` or `stride` is less than or equal to `0`, the function returns `x` unchanged.
#### sscal.ndarray( N, alpha, x, stride, offset )
Multiplies a single-precision floating-point vector `x` by a constant `alpha` using alternative indexing semantics.
```javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
sscal.ndarray( x.length, 5.0, x, 1, 0 );
// x => [ -10.0, 5.0, 15.0, -25.0, 20.0, 0.0, -5.0, -15.0 ]
```
The function has the following additional parameters:
- **offset**: 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 multiply the last three elements of `x` by a constant
```javascript
var Float32Array = require( '@stdlib/array-float32' );
var x = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
sscal.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => [ 1.0, -2.0, 3.0, -20.0, 25.0, -30.0 ]
```
## Notes
- If `N <= 0`, both functions return `x` unchanged.
- `sscal()` corresponds to the [BLAS][blas] level 1 function [`sscal`][sscal].
## Examples
```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var sscal = require( '@stdlib/blas-base-sscal' );
var opts = {
'dtype': 'float32'
};
var x = discreteUniform( 10, -100, 100, opts );
console.log( x );
sscal( x.length, 5.0, x, 1 );
console.log( x );
```
* * *
## See Also
- [`@stdlib/blas-base/daxpy`][@stdlib/blas/base/daxpy]: multiply a vector x by a constant and add the result to y.
- [`@stdlib/blas-base/dscal`][@stdlib/blas/base/dscal]: multiply a double-precision floating-point vector by a constant.
- [`@stdlib/blas-base/gscal`][@stdlib/blas/base/gscal]: multiply a vector by a constant.
- [`@stdlib/blas-base/saxpy`][@stdlib/blas/base/saxpy]: multiply a vector x by a constant and add the result to y.
* * *
## 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 © 2016-2024. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-base-sscal.svg
[npm-url]: https://npmjs.org/package/@stdlib/blas-base-sscal
[test-image]: https://github.com/stdlib-js/blas-base-sscal/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/blas-base-sscal/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-sscal/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-sscal?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-base-sscal/tree/deno
[deno-readme]: https://github.com/stdlib-js/blas-base-sscal/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/blas-base-sscal/tree/umd
[umd-readme]: https://github.com/stdlib-js/blas-base-sscal/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/blas-base-sscal/tree/esm
[esm-readme]: https://github.com/stdlib-js/blas-base-sscal/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/blas-base-sscal/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-base-sscal/main/LICENSE
[blas]: http://www.netlib.org/blas
[sscal]: http://www.netlib.org/lapack/explore-html/df/d28/group__single__blas__level1.html
[@stdlib/array/float32]: https://github.com/stdlib-js/array-float32
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@stdlib/blas/base/daxpy]: https://github.com/stdlib-js/blas-base-daxpy
[@stdlib/blas/base/dscal]: https://github.com/stdlib-js/blas-base-dscal
[@stdlib/blas/base/gscal]: https://github.com/stdlib-js/blas-base-gscal
[@stdlib/blas/base/saxpy]: https://github.com/stdlib-js/blas-base-saxpy