@stdlib/blas-ext-base-srev

Reverse a single-precision floating-point strided array in-place.

https://github.com/stdlib-js/blas-ext-base-srev

Science Score: 44.0%

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Keywords

array blas extended flip float float32 float32array javascript math mathematics ndarray node node-js nodejs rev reverse single stdlib strided swap

Last synced: 4 months ago · JSON representation ·

Repository

Reverse a single-precision floating-point strided array in-place.

Basic Info

Host: GitHub
Owner: stdlib-js
License: apache-2.0
Language: JavaScript
Default Branch: main
Homepage: https://github.com/stdlib-js/stdlib
Size: 562 KB

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Stars: 2
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array blas extended flip float float32 float32array javascript math mathematics ndarray node node-js nodejs rev reverse single stdlib strided swap

Created over 4 years ago · Last pushed 6 months ago

Metadata Files

Readme Changelog Contributing License Code of conduct Citation Security

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

srev

Reverse a single-precision floating-point strided array in-place.

## Installation ```bash npm install @stdlib/blas-ext-base-srev ``` 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 srev = require( '@stdlib/blas-ext-base-srev' ); ``` #### srev( N, x, strideX ) Reverses a single-precision floating-point strided array in-place. ```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 ] ); srev( x.length, x, 1 ); // x => [ -3.0, -1.0, 0.0, 4.0, -5.0, 3.0, 1.0, -2.0 ] ``` The function has the following parameters: - **N**: number of indexed elements. - **x**: input [`Float32Array`][@stdlib/array/float32]. - **strideX**: stride length. The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to reverse every other element: ```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 ] ); srev( 4, x, 2 ); // x => [ -1.0, 1.0, 4.0, -5.0, 3.0, 0.0, -2.0, -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 // Reverse every other element... srev( 3, x1, 2 ); // x0 => [ 1.0, -6.0, 3.0, -4.0, 5.0, -2.0 ] ``` #### srev.ndarray( N, x, strideX, offsetX ) Reverses a single-precision floating-point strided array in-place 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 ] ); srev.ndarray( x.length, x, 1, 0 ); // x => [ -3.0, -1.0, 0.0, 4.0, -5.0, 3.0, 1.0, -2.0 ] ``` 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 access only the last three elements of the strided array: ```javascript var Float32Array = require( '@stdlib/array-float32' ); var x = new Float32Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] ); srev.ndarray( 3, x, 1, x.length-3 ); // x => [ 1.0, -2.0, 3.0, -6.0, 5.0, -4.0 ] ```

## Notes - If `N <= 0`, both functions return the strided array unchanged. - Where possible, one should "reverse" a strided array by negating its stride, which is an `O(1)` operation, in contrast to performing an in-place reversal, which is `O(N)`. However, in certain circumstances, this is not tenable, particularly when interfacing with libraries which assume and/or expect a specific memory layout (e.g., strided array elements arranged in memory in ascending order). In general, when working with strided arrays, only perform an in-place reversal when strictly necessary.

## Examples ```javascript var discreteUniform = require( '@stdlib/random-array-discrete-uniform' ); var srev = require( '@stdlib/blas-ext-base-srev' ); var x = discreteUniform( 10, -100, 100, { 'dtype': 'float32' }); console.log( x ); srev( x.length, x, 1 ); console.log( x ); ```

## C APIs

### Usage ```c #include "stdlib/blas/ext/base/srev.h" ``` #### stdlib_strided_srev( N, \*X, strideX ) Reverses a single-precision floating-point strided array in-place. ```c float x[] = { 1.0f, 2.0f, 3.0f, 4.0f }; stdlib_strided_srev( 4, x, 1 ); ``` The function accepts the following arguments: - **N**: `[in] CBLAS_INT` number of indexed elements. - **X**: `[inout] float*` input array. - **strideX**: `[in] CBLAS_INT` stride length. ```c void stdlib_strided_srev( const CBLAS_INT N, float *X, const CBLAS_INT strideX ); ``` #### stdlib_strided_srev_ndarray( N, \*X, strideX, offsetX ) Reverses a single-precision floating-point strided array in-place using alternative indexing semantics. ```c float x[] = { 1.0f, 2.0f, 3.0f, 4.0f }; stdlib_strided_srev_ndarray( 4, x, 1, 0 ); ``` The function accepts the following arguments: - **N**: `[in] CBLAS_INT` number of indexed elements. - **X**: `[inout] float*` input array. - **strideX**: `[in] CBLAS_INT` stride length. - **offsetX**: `[in] CBLAS_INT` starting index. ```c void stdlib_strided_srev_ndarray( const CBLAS_INT N, float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX ); ```

### Examples ```c #include "stdlib/blas/ext/base/srev.h" #include int main( void ) { // Create a strided array: float x[] = { 1.0f, -2.0f, 3.0f, -4.0f, 5.0f, -6.0f, 7.0f, -8.0f }; // Specify the number of elements: const int N = 8; // Specify a stride: const int strideX = 1; // Reverse the array: stdlib_strided_srev( N, x, strideX ); // Print the result: for ( int i = 0; i < 8; i++ ) { printf( "x[ %i ] = %f\n", i, x[ i ] ); } } ```

* * * ## 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].

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Standard library for JavaScript.

Citation (CITATION.cff)

cff-version: 1.2.0
title: stdlib
message: >-
  If you use this software, please cite it using the
  metadata from this file.

type: software

authors:
  - name: The Stdlib Authors
    url: https://github.com/stdlib-js/stdlib/graphs/contributors

repository-code: https://github.com/stdlib-js/stdlib
url: https://stdlib.io

abstract: |
  Standard library for JavaScript and Node.js.

keywords:
  - JavaScript
  - Node.js
  - TypeScript
  - standard library
  - scientific computing
  - numerical computing
  - statistical computing

license: Apache-2.0 AND BSL-1.0

date-released: 2016

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npmjs.org: @stdlib/blas-ext-base-srev

Reverse a single-precision floating-point strided array in-place.

Homepage: https://stdlib.io
License: Apache-2.0
Latest release: 0.2.2
published over 1 year ago

Versions: 15
Dependent Packages: 3
Dependent Repositories: 2
Downloads: 16 Last month

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Dependent packages count: 5.9%

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Average: 11.3%

Downloads: 12.9%

Stargazers count: 14.5%

Forks count: 15.4%

Maintainers (4)

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@stdlib/assert-is-browser ^0.0.x development
@stdlib/bench ^0.0.x development
@stdlib/math-base-assert-is-nanf ^0.0.x development
@stdlib/math-base-special-pow ^0.0.x development
@stdlib/math-base-special-round ^0.0.x development
@stdlib/random-base-randu ^0.0.x development
istanbul ^0.4.1 development
proxyquire ^2.0.0 development
tap-spec 5.x.x development
tape git+https://github.com/kgryte/tape.git#fix/globby development
@stdlib/assert-is-error ^0.0.x
@stdlib/math-base-special-floor ^0.0.x
@stdlib/utils-define-nonenumerable-read-only-property ^0.0.x
@stdlib/utils-library-manifest ^0.0.x
@stdlib/utils-try-require ^0.0.x

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@stdlib/blas-ext-base-srev

Science Score: 44.0%

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