About stdlib...

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!

drev

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]

> Reverse a double-precision floating-point strided array in-place.

Installation

``bash npm install @stdlib/blas-ext-base-drev`

`Usage`

`javascript var drev = require( '@stdlib/blas-ext-base-drev' );`

#### drev( N, x, strideX )

Reverses a double-precision floating-point strided array x in-place.

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev( 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 [Float64Array][@stdlib/array/float64]. - strideX: stride length forx.

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 Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev( 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 Float64Array = require( '@stdlib/array-float64' );

// Initial array... var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

// Create an offset view... var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Reverse every other element... drev( 3, x1, 2 ); // x0 => [ 1.0, -6.0, 3.0, -4.0, 5.0, -2.0 ]`

#### drev.ndarray( N, x, strideX, offsetX )

Reverses a double-precision floating-point strided array x in-place using alternative indexing semantics.

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev.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 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 access only the last three elements of the strided array:

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

drev.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 anO(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 drev = require( '@stdlib/blas-ext-base-drev' );

var x = discreteUniform( 10, -100, 100, { 'dtype': 'float64' }); console.log( x );

drev( x.length, x, 1 ); console.log( x );`

*

`C APIs`

`$3`

`c #include "stdlib/blas/ext/base/drev.h"`

#### stdlib_strided_drev( N, \*X, strideX )

Reverses a double-precision floating-point strided array X in-place.

`c double x[] = { 1.0, 2.0, 3.0, 4.0 };

stdlib_strided_drev( 4, x, 1 );`

The function accepts the following arguments:

- N: [in] CBLAS_INTnumber of indexed elements. - X:[inout] double*input array. - strideX:[in] CBLAS_INT stride length for X.

`c double stdlib_strided_drev( const CBLAS_INT N, double *X, const CBLAS_INT strideX );`

#### stdlib_strided_drev_ndarray( N, \*X, strideX, offsetX )

Reverses a double-precision floating-point strided array X in-place using alternative indexing semantics.

`c double x[] = { 1.0, 2.0, 3.0, 4.0 };

stdlib_strided_drev_ndarray( 4, x, 1, 0 );`

The function accepts the following arguments:

- N: [in] CBLAS_INTnumber of indexed elements. - X:[inout] double*input array. - strideX:[in] CBLAS_INT stride length for X. - offsetX:[in] CBLAS_INT starting index for X.

`c void stdlib_strided_drev_ndarray( const CBLAS_INT N, double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );`

`$3`

`c #include "stdlib/blas/ext/base/drev.h" #include

int main( void ) { // Create a strided array: double x[] = { 1.0, -2.0, 3.0, -4.0, 5.0, -6.0, 7.0, -8.0 };

// Specify the number of elements: const int N = 8;

// Specify a stride: const int strideX = 1;

// Reverse the array: stdlib_strided_drev( N, x, strideX );

// Print the result: for ( int i = 0; i < 8; i++ ) { printf( "x[ %i ] = %lf\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`

[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-ext-base-drev.svg [npm-url]: https://npmjs.org/package/@stdlib/blas-ext-base-drev

[test-image]: https://github.com/stdlib-js/blas-ext-base-drev/actions/workflows/test.yml/badge.svg?branch=v0.3.1 [test-url]: https://github.com/stdlib-js/blas-ext-base-drev/actions/workflows/test.yml?query=branch:v0.3.1

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-ext-base-drev/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/blas-ext-base-drev?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-drev/tree/deno [deno-readme]: https://github.com/stdlib-js/blas-ext-base-drev/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/blas-ext-base-drev/tree/umd [umd-readme]: https://github.com/stdlib-js/blas-ext-base-drev/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/blas-ext-base-drev/tree/esm [esm-readme]: https://github.com/stdlib-js/blas-ext-base-drev/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/blas-ext-base-drev/blob/main/branches.md

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-base-drev/main/LICENSE

[@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/blas/ext/base/grev]: https://www.npmjs.com/package/@stdlib/blas-ext-base-grev

[@stdlib/blas/ext/base/srev]: https://www.npmjs.com/package/@stdlib/blas-ext-base-srev


  
    About stdlib...
  

  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!

`drev`

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]

> Reverse a double-precision floating-point strided array in-place.

`Installation`

``bash npm install @stdlib/blas-ext-base-drev `

`Usage`

`javascript var drev = require( '@stdlib/blas-ext-base-drev' ); `

#### drev( N, x, strideX )

Reverses a double-precision floating-point strided array x in-place.

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev( 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 [Float64Array][@stdlib/array/float64]. - strideX: stride length for x.

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 Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev( 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 Float64Array = require( '@stdlib/array-float64' );

// Initial array... var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

// Create an offset view... var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Reverse every other element... drev( 3, x1, 2 ); // x0 => [ 1.0, -6.0, 3.0, -4.0, 5.0, -2.0 ] `

#### drev.ndarray( N, x, strideX, offsetX )

Reverses a double-precision floating-point strided array x in-place using alternative indexing semantics.

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );

drev.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 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 access only the last three elements of the strided array:

`javascript var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );

drev.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 drev = require( '@stdlib/blas-ext-base-drev' );

var x = discreteUniform( 10, -100, 100, { 'dtype': 'float64' }); console.log( x );

drev( x.length, x, 1 ); console.log( x ); `

*

`C APIs`

`$3`

`c #include "stdlib/blas/ext/base/drev.h" `

#### stdlib_strided_drev( N, \*X, strideX )

Reverses a double-precision floating-point strided array X in-place.

`c double x[] = { 1.0, 2.0, 3.0, 4.0 };

stdlib_strided_drev( 4, x, 1 ); `

The function accepts the following arguments:

- N: [in] CBLAS_INT number of indexed elements. - X: [inout] double* input array. - strideX: [in] CBLAS_INT stride length for X.

`c double stdlib_strided_drev( const CBLAS_INT N, double *X, const CBLAS_INT strideX ); `

#### stdlib_strided_drev_ndarray( N, \*X, strideX, offsetX )

Reverses a double-precision floating-point strided array X in-place using alternative indexing semantics.

`c double x[] = { 1.0, 2.0, 3.0, 4.0 };

stdlib_strided_drev_ndarray( 4, x, 1, 0 ); `

The function accepts the following arguments:

- N: [in] CBLAS_INT number of indexed elements. - X: [inout] double* input array. - strideX: [in] CBLAS_INT stride length for X. - offsetX: [in] CBLAS_INT starting index for X.

`c void stdlib_strided_drev_ndarray( const CBLAS_INT N, double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX ); `

`$3`

`c #include "stdlib/blas/ext/base/drev.h" #include

int main( void ) { // Create a strided array: double x[] = { 1.0, -2.0, 3.0, -4.0, 5.0, -6.0, 7.0, -8.0 };

// Specify the number of elements: const int N = 8;

// Specify a stride: const int strideX = 1;

// Reverse the array: stdlib_strided_drev( N, x, strideX );

// Print the result: for ( int i = 0; i < 8; i++ ) { printf( "x[ %i ] = %lf\n", i, x[ i ] ); } } `

*

`Notice`

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`

[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-ext-base-drev.svg [npm-url]: https://npmjs.org/package/@stdlib/blas-ext-base-drev

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-ext-base-drev/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/blas-ext-base-drev?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

[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-ext-base-drev/main/LICENSE

[@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/blas/ext/base/grev]: https://www.npmjs.com/package/@stdlib/blas-ext-base-grev

[@stdlib/blas/ext/base/srev]: https://www.npmjs.com/package/@stdlib/blas-ext-base-srev

@stdlib/blas-ext-base-drev

drev

Installation

Usage

Notes

Examples

C APIs

$3

$3

See Also

Notice

License

Copyright

@stdlib/blas-ext-base-drev

drev

Installation

Usage

Notes

Examples

C APIs

$3

$3

See Also

Notice

License

Copyright

`Usage`

`Notes`

`Examples`

`C APIs`

`$3`

`$3`

`See Also`

`Notice`

`License`

`Copyright`

`@stdlib/blas-ext-base-drev`

`drev`

`Installation`

`Usage`

`Notes`

`Examples`

`C APIs`

`$3`

`$3`

`See Also`

`Notice`

`License`

`Copyright`