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https://github.com/stdlib-js/blas-base-drot-wasm

Applies a plane rotation.
https://github.com/stdlib-js/blas-base-drot-wasm

algebra array blas double drot float64 float64array javascript level-1 linear math mathematics ndarray node node-js nodejs rotation stdlib subroutines vector

Last synced: 8 days ago
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Applies a plane rotation.

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README 

        



  

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# drot



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



> Apply a plane rotation.



## Installation



```bash

npm install @stdlib/blas-base-drot-wasm

```



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 drot = require( '@stdlib/blas-base-drot-wasm' );

```



#### drot.main( N, x, strideX, y, strideY, c, s )



Applies a plane rotation.



```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( [ 1.0, 1.0, 1.0, 1.0, 1.0 ] );



drot.main( x.length, x, 1, y, 1, 0.0, 1.0 );

// x => [ 1.0, 1.0, 1.0, 1.0, 1.0 ]

// y => [ -1.0, -2.0, -3.0, -4.0, -5.0 ]

```



The function has the following parameters:



-   **N**: number of indexed elements.

-   **x**: input [`Float64Array`][@stdlib/array/float64].

-   **strideX**: index increment for `x`.

-   **y**: input [`Float64Array`][@stdlib/array/float64].

-   **strideY**: index increment for `y`.

-   **c**: cosine of the angle of rotation.

-   **s**: sine of the angle of rotation.



The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to apply a plane rotation to every other element,



```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 ] );



drot.main( 3, x, 2, y, 2, 0.8, 0.6 );

// x => [ 5.0, 2.0, 7.8, 4.0, 10.6, 6.0 ]

// y => [ ~5.0, 8.0, 5.4, 10.0, ~5.8, 12.0 ]

```



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 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



drot.main( 3, x1, -2, y1, 1, 0.8, 0.6 );

// x0 => [ 1.0, ~8.8, 3.0, 9.8, 5.0, 10.8 ]

// y0 => [ 7.0, 8.0, 9.0, 4.4, 6.4, ~8.4 ]

```



#### drot.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, c, s )



Applies a plane rotation 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 ] );



drot.ndarray( 4, x, 1, 1, y, 1, 1, 0.8, 0.6 );

// x => [ 1.0, ~5.8, 7.2, 8.6, 10.0 ]

// y => [ 6.0, 4.4, ~4.6, ~4.8, 5.0 ]

```



The function has the following additional parameters:



-   **offsetX**: starting index for `x`.

-   **offsetY**: starting index for `y`.



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 apply a plane rotation to every other element starting from the second element,



```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 ] );



drot.ndarray( 3, x, 2, 1, y, 2, 1, 0.8, 0.6 );

// x => [ 1.0, 6.4, 3.0, 9.2, 5.0, 12.0 ]

// y => [ 7.0, 5.2, 9.0, 5.6, 11.0, ~6.0 ]

```



* * *



### Module



#### drot.Module( memory )



Returns a new WebAssembly [module wrapper][@stdlib/wasm/module-wrapper] instance which uses the provided WebAssembly [memory][@stdlib/wasm/memory] instance as its underlying memory.



```javascript

var Memory = require( '@stdlib/wasm-memory' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new drot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();

```



#### drot.Module.prototype.main( N, xp, sx, yp, sy, c, s )



Applies a plane rotation.



```javascript

var Memory = require( '@stdlib/wasm-memory' );

var oneTo = require( '@stdlib/array-one-to' );

var ones = require( '@stdlib/array-ones' );

var zeros = require( '@stdlib/array-zeros' );

var bytesPerElement = require( '@stdlib/ndarray-base-bytes-per-element' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new drot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();



// Define a vector data type:

var dtype = 'float64';



// Specify a vector length:

var N = 5;



// Define pointers (i.e., byte offsets) for storing two vectors:

var xptr = 0;

var yptr = N * bytesPerElement( dtype );



// Write vector values to module memory:

mod.write( xptr, oneTo( N, dtype ) );

mod.write( yptr, ones( N, dtype ) );



// Perform computation:

mod.main( N, xptr, 1, yptr, 1, 0.0, 1.0 );



// Read out the results:

var viewX = zeros( N, dtype );

var viewY = zeros( N, dtype );

mod.read( xptr, viewX );

mod.read( yptr, viewY );



console.log( viewX );

// => [ 1.0, 1.0, 1.0, 1.0, 1.0 ]



console.log( viewY );

// => [ -1.0, -2.0, -3.0, -4.0, -5.0 ]

```



The function has the following parameters:



-   **N**: number of indexed elements.

-   **xp**: input [`Float64Array`][@stdlib/array/float64] pointer (i.e., byte offset).

-   **sx**: index increment for `x`.

-   **yp**: input [`Float64Array`][@stdlib/array/float64] pointer (i.e., byte offset).

-   **sy**: index increment for `y`.

-   **c**: cosine of the angle of rotation.

-   **s**: sine of the angle of rotation.



#### drot.Module.prototype.ndarray( N, xp, sx, ox, yp, sy, oy, c, s )



Applies a plane rotation using alternative indexing semantics.



```javascript

var Memory = require( '@stdlib/wasm-memory' );

var oneTo = require( '@stdlib/array-one-to' );

var ones = require( '@stdlib/array-ones' );

var zeros = require( '@stdlib/array-zeros' );

var bytesPerElement = require( '@stdlib/ndarray-base-bytes-per-element' );



// Create a new memory instance with an initial size of 10 pages (640KiB) and a maximum size of 100 pages (6.4MiB):

var mem = new Memory({

    'initial': 10,

    'maximum': 100

});



// Create a BLAS routine:

var mod = new drot.Module( mem );

// returns 



// Initialize the routine:

mod.initializeSync();



// Define a vector data type:

var dtype = 'float64';



// Specify a vector length:

var N = 5;



// Define pointers (i.e., byte offsets) for storing two vectors:

var xptr = 0;

var yptr = N * bytesPerElement( dtype );



// Write vector values to module memory:

mod.write( xptr, oneTo( N, dtype ) );

mod.write( yptr, ones( N, dtype ) );



// Perform computation:

mod.ndarray( N, xptr, 1, 0, yptr, 1, 0, 0.0, 1.0 );



// Read out the results:

var viewX = zeros( N, dtype );

var viewY = zeros( N, dtype );

mod.read( xptr, viewX );

mod.read( yptr, viewY );



console.log( viewX );

// => [ 1.0, 1.0, 1.0, 1.0, 1.0 ]



console.log( viewY );

// => [ -1.0, -2.0, -3.0, -4.0, -5.0 ]

```



The function has the following additional parameters:



-   **ox**: starting index for `x`.

-   **oy**: starting index for `y`.



* * *



## Notes



-   If `N <= 0`, both vectors are unchanged.

-   This package implements routines using WebAssembly. When provided arrays which are not allocated on a `drot` module memory instance, data must be explicitly copied to module memory prior to computation. Data movement may entail a performance cost, and, thus, if you are using arrays external to module memory, you should prefer using [`@stdlib/blas-base/drot`][@stdlib/blas/base/drot]. However, if working with arrays which are allocated and explicitly managed on module memory, you can achieve better performance when compared to the pure JavaScript implementations found in [`@stdlib/blas/base/drot`][@stdlib/blas/base/drot]. Beware that such performance gains may come at the cost of additional complexity when having to perform manual memory management. Choosing between implementations depends heavily on the particular needs and constraints of your application, with no one choice universally better than the other.

-   `drot()` corresponds to the [BLAS][blas] level 1 function [`drot`][drot].



* * *



## Examples



```javascript

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );

var drot = require( '@stdlib/blas-base-drot-wasm' );



var opts = {

    'dtype': 'float64'

};

var x = discreteUniform( 10, 0, 100, opts );

console.log( x );



var y = discreteUniform( x.length, 0, 10, opts );

console.log( y );



drot.ndarray( x.length, x, 1, 0, y, -1, y.length-1, 0.8, 0.6 );

console.log( 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-drot-wasm.svg

[npm-url]: https://npmjs.org/package/@stdlib/blas-base-drot-wasm



[test-image]: https://github.com/stdlib-js/blas-base-drot-wasm/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/blas-base-drot-wasm/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-drot-wasm/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-drot-wasm?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-drot-wasm/tree/deno

[deno-readme]: https://github.com/stdlib-js/blas-base-drot-wasm/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/blas-base-drot-wasm/tree/umd

[umd-readme]: https://github.com/stdlib-js/blas-base-drot-wasm/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/blas-base-drot-wasm/tree/esm

[esm-readme]: https://github.com/stdlib-js/blas-base-drot-wasm/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/blas-base-drot-wasm/blob/main/branches.md



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



[blas]: http://www.netlib.org/blas



[drot]: https://www.netlib.org/lapack/explore-html/d1/d45/group__rot_gae48ef017306866ac2d5a8c5a52617858.html#gae48ef017306866ac2d5a8c5a52617858



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



[@stdlib/array/float64]: https://github.com/stdlib-js/array-float64



[@stdlib/wasm/memory]: https://github.com/stdlib-js/wasm-memory



[@stdlib/wasm/module-wrapper]: https://github.com/stdlib-js/wasm-module-wrapper



[@stdlib/blas/base/drot]: https://github.com/stdlib-js/blas-base-drot