Interchange two double-precision floating-point vectors.
npm install @stdlib/blas-base-dswapWe 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!
About stdlib...
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Interchange two double-precision floating-point vectors.
``bash`
npm install @stdlib/blas-base-dswap
`javascript`
var dswap = require( '@stdlib/blas-base-dswap' );
#### dswap( N, x, strideX, y, strideY )
Interchanges vectors x and y.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
dswap( x.length, x, 1, y, 1 );
// x =>
// y =>
`
The function has the following parameters:
- N: number of indexed elements.
- x: first input [Float64Array][mdn-float64array].x
- strideX: index increment for .Float64Array
- y: second input [][mdn-float64array].y
- strideY: index increment for .
The N and stride parameters determine how values in the strided arrays are accessed at runtime. For example, to swap in reverse order every other value in x with the first N elements of y,
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
dswap( 3, x, -2, y, 1 );
// x =>
// y =>
`
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 arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
// Swap in reverse order every other value from x1 with y1...`
dswap( 3, x1, -2, y1, 1 );
// x0 =>
// y0 =>
#### dswap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )
Interchanges vectors x and y using alternative indexing semantics.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
dswap.ndarray( x.length, x, 1, 0, y, 1, 0 );
// x =>
// y =>
`
The function has the following additional parameters:
- offsetX: starting index for x.y
- offsetY: starting index for .
While [typed array][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to swap every other value in x starting from the second value with the last N elements in y where x[i] = y[n], x[i+2] = y[n-1],...,
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
dswap.ndarray( 3, x, 2, 1, y, -1, y.length-1 );
// x =>
// y =>
`
- If N <= 0, both functions leave x and y unchanged.dswap()
- corresponds to the [BLAS][blas] level 1 function [dswap][dswap].
`javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var dswap = require( '@stdlib/blas-base-dswap' );
var opts = {
'dtype': 'float64'
};
var x = discreteUniform( 10, 0, 500, opts );
console.log( x );
var y = discreteUniform( x.length, 0, 255, opts );
console.log( y );
// Swap elements in x and y starting from the end of y:`
dswap( x.length, x, 1, y, -1 );
console.log( x );
console.log( y );
*
`c`
#include "stdlib/blas/base/dswap.h"
#### c_dswap( N, \X, strideX, \Y, strideY )
Interchanges two double-precision floating-point vectors.
`c
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
double y[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
c_dswap( 5, x, 1, y, 1 );
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[inout] double*
- X: first input array.[in] CBLAS_INT
- strideX: index increment for X.[inout] double*
- Y: second input array.[in] CBLAS_INT
- strideY: index increment for Y.
`c`
void c_dswap( const CBLAS_INT N, double X, const CBLAS_INT strideX, double Y, const CBLAS_INT strideY );
#### c_dswap_ndarray( N, \X, strideX, offsetX, \Y, strideY, offsetY )
Interchanges two double-precision floating-point vectors using alternative indexing semantics.
`c
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
double y[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
c_dswap_ndarray( 3, x, 1, 2, y, 1, 2 );
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[inout] double*
- X: first input array.[in] CBLAS_INT
- strideX: index increment for X.[in] CBLAS_INT
- offsetX: starting index for X.[inout] double*
- Y: second input array.[in] CBLAS_INT
- strideY: index increment for Y.[in] CBLAS_INT
- offsetY: starting index for Y.
`c`
void c_dswap_ndarray( const CBLAS_INT N, double X, const CBLAS_INT strideX, const CBLAS_INT offsetX, double Y, const CBLAS_INT strideY, const CBLAS_INT offsetY );
`c
#include "stdlib/blas/base/dswap.h"
#include
int main( void ) {
// Create strided arrays:
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
double y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
// Specify the number of indexed elements:
const int N = 4;
// Specify stride lengths:
const int strideX = 2;
const int strideY = -2;
// Interchange elements:
c_dswap( N, x, strideX, y, strideY );
// Print the result:
for ( int i = 0; i < 8; i++ ) {
printf( "x[ %i ] = %lf\n", i, x[ i ] );
printf( "y[ %i ] = %lf\n", i, y[ i ] );
}
// Interchange elements:
c_dswap_ndarray( N, x, strideX, 0, y, strideY, 6 );
// Print the result:
for ( int i = 0; i < 8; i++ ) {
printf( "x[ %i ] = %lf\n", i, x[ i ] );
printf( "y[ %i ] = %lf\n", i, y[ i ] );
}
}
`
*
- [@stdlib/blas-base/dcopy][@stdlib/blas/base/dcopy]: copy values from x into y.
- [@stdlib/blas-base/gswap][@stdlib/blas/base/gswap]: interchange two vectors.
- [@stdlib/blas-base/sswap][@stdlib/blas/base/sswap]: interchange two single-precision floating-point vectors.
- [@stdlib/blas-dswap][@stdlib/blas/dswap]: interchange two double-precision floating-point vectors.
*
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]
---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/blas-base-dswap.svg
[npm-url]: https://npmjs.org/package/@stdlib/blas-base-dswap
[test-image]: https://github.com/stdlib-js/blas-base-dswap/actions/workflows/test.yml/badge.svg?branch=v0.4.1
[test-url]: https://github.com/stdlib-js/blas-base-dswap/actions/workflows/test.yml?query=branch:v0.4.1
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-dswap/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-dswap?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-base-dswap/tree/deno
[deno-readme]: https://github.com/stdlib-js/blas-base-dswap/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/blas-base-dswap/tree/umd
[umd-readme]: https://github.com/stdlib-js/blas-base-dswap/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/blas-base-dswap/tree/esm
[esm-readme]: https://github.com/stdlib-js/blas-base-dswap/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/blas-base-dswap/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-base-dswap/main/LICENSE
[blas]: http://www.netlib.org/blas
[dswap]: http://www.netlib.org/lapack/explore-html/de/da4/group__double__blas__level1.html
[mdn-float64array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@stdlib/blas/base/dcopy]: https://www.npmjs.com/package/@stdlib/blas-base-dcopy
[@stdlib/blas/base/gswap]: https://www.npmjs.com/package/@stdlib/blas-base-gswap
[@stdlib/blas/base/sswap]: https://www.npmjs.com/package/@stdlib/blas-base-sswap
[@stdlib/blas/dswap]: https://www.npmjs.com/package/@stdlib/blas-dswap