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https://github.com/stdlib-js/blas-base-dznrm2

Compute the L2-norm of a complex double-precision floating-point vector.
https://github.com/stdlib-js/blas-base-dznrm2

algebra array blas dznrm2 euclidean euclidean-norm float64 javascript level-1 linear math mathematics ndarray node node-js nodejs norm stdlib subroutines vector

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Compute the L2-norm of a complex double-precision floating-point vector.

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README 

        



  

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# dznrm2



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



> Compute the L2-norm of a complex double-precision floating-point vector.



## Installation



```bash

npm install @stdlib/blas-base-dznrm2

```



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 dznrm2 = require( '@stdlib/blas-base-dznrm2' );

```



#### dznrm2( N, zx, strideX )



Computes the L2-norm of a complex double-precision floating-point vector.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );



var zx = new Complex128Array( [ 0.3, 0.1, 0.5, 0.0, 0.0, 0.5, 0.0, 0.2 ] );



var norm = dznrm2( 4, zx, 1 );

// returns ~0.8

```



The function has the following parameters:



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

-   **zx**: input [`Complex128Array`][@stdlib/array/complex128].

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



The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to traverse every other value,



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );



var zx = new Complex128Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );



var norm = dznrm2( 2, zx, 2 );

// returns ~4.6

```



Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );



// Initial array:

var zx0 = new Complex128Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );



// Create an offset view:

var zx1 = new Complex128Array( zx0.buffer, zx0.BYTES_PER_ELEMENT*1 ); // start at 2nd element



// Compute the L2-norm:

var norm = dznrm2( 2, zx1, 1 );

// returns ~9.3

```



#### dznrm2.ndarray( N, zx, strideX, offset )



Computes the L2-norm of a complex double-precision floating-point vector using alternative indexing semantics.



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );



var zx = new Complex128Array( [ 0.3, 0.1, 0.5, 0.0, 0.0, 0.5, 0.0, 0.2 ] );



var norm = dznrm2.ndarray( 4, zx, 1, 0 );

// returns ~0.8

```



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 start from the second index,



```javascript

var Complex128Array = require( '@stdlib/array-complex128' );



var zx = new Complex128Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );



var norm = dznrm2.ndarray( 2, zx, 1, 1 );

// returns ~9.3

```



## Notes



-   If `N <= 0`, both functions return `0.0`.

-   `dznrm2()` corresponds to the [BLAS][blas] level 1 function [`dznrm2`][dznrm2].



## Examples



```javascript

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

var filledarrayBy = require( '@stdlib/array-filled-by' );

var Complex128 = require( '@stdlib/complex-float64-ctor' );

var dznrm2 = require( '@stdlib/blas-base-dznrm2' );



function rand() {

    return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );

}



var zx = filledarrayBy( 10, 'complex128', rand );

console.log( zx.toString() );



// Computes the L2-norm:

var norm = dznrm2( zx.length, zx, 1 );

console.log( norm );

```



* * *



## C APIs



### Usage



```c

#include "stdlib/blas/base/dznrm2.h"

```



#### c_dznrm2( N, \*ZX, strideX )



Computes the L2-norm of a complex double-precision floating-point vector.



```c

const double zx[] = { 0.3, 0.1, 0.5, 0.0, 0.0, 0.5, 0.0, 0.2 };



double norm = c_dznrm2( 4, (void *)zx, 1 );

// returns 0.8

```



The function accepts the following arguments:



-   **N**: `[in] CBLAS_INT` number of indexed elements.

-   **ZX**: `[in] void*` input array.

-   **strideX**: `[in] CBLAS_INT` index increment for `ZX`.



```c

double c_dznrm2( const CBLAS_INT N, const void *ZX, const CBLAS_INT strideX );

```



### Examples



```c

#include "stdlib/blas/base/dznrm2.h"

#include 



int main( void ) {

    // Create a strided array of interleaved real and imaginary components:

    const double zx[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };



    // Specify the number of elements:

    const int N = 4;



    // Specify stride length:

    const int strideX = 1;



    // Compute the L2-norm:

    c_dznrm2( N, (void *)zx, strideX );



    // Print the result:

    printf( "L2-norm: %lf\n", norm );

}

```



* * *



## 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-dznrm2.svg

[npm-url]: https://npmjs.org/package/@stdlib/blas-base-dznrm2



[test-image]: https://github.com/stdlib-js/blas-base-dznrm2/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/blas-base-dznrm2/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/blas-base-dznrm2/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/blas-base-dznrm2?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-dznrm2/tree/deno

[deno-readme]: https://github.com/stdlib-js/blas-base-dznrm2/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/blas-base-dznrm2/tree/umd

[umd-readme]: https://github.com/stdlib-js/blas-base-dznrm2/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/blas-base-dznrm2/tree/esm

[esm-readme]: https://github.com/stdlib-js/blas-base-dznrm2/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/blas-base-dznrm2/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/blas-base-dznrm2/main/LICENSE



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



[dznrm2]: https://netlib.org/lapack/explore-html//d1/d2a/group__nrm2_ga7f9f9febc6dc1836c9f5e7c1aa00b743.html



[@stdlib/array/complex128]: https://github.com/stdlib-js/array-complex128



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