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zscal

Scales a double-precision complex floating-point vector by a double-precision complex floating-point constant.

Installation

npm install @stdlib/blas-base-zscal

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md 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

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

zscal( N, alpha, x, strideX )

Scales values from x by alpha.

var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
var alpha = new Complex128( 2.0, 0.0 );

zscal( 3, alpha, x, 1 );
// x => <Complex128Array>[ 2.0, 2.0, 2.0, 2.0, 2.0, 2.0 ]

The function has the following parameters:

• N: number of indexed elements.
• alpha: scalar Complex128 constant.
• x: input Complex128Array.
• strideX: index increment for x.

The N and stride parameters determine how values from x are scaled by alpha. For example, to scale every other value in x by alpha,

var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var alpha = new Complex128( 2.0, 0.0 );

zscal( 2, alpha, x, 2 );
// x => <Complex128Array>[ 2.0, 4.0, 3.0, 4.0, 10.0, 12.0, 7.0, 8.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

// Initial array:
var x0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

// Define a scalar constant:
var alpha = new Complex128( 2.0, 2.0 );

// Create an offset view:
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Scales every other value from `zx1` by `za`...
zscal( 3, alpha, x1, 1 );
// x0 => <Complex128Array>[ 1.0, 2.0, -2.0, 14.0, -2.0, 22.0, -2.0, 30.0 ]

zscal.ndarray( N, alpha, x, strideX, offsetX )

Scales values from x by alpha using alternative indexing semantics.

var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var alpha = new Complex128( 2.0, 2.0 );

zscal.ndarray( 3, alpha, x, 1, 0 );
// x => <Complex128Array>[ -2.0, 6.0, -2.0, 14.0, -2.0, 22.0 ]

The function has the following additional parameters:

• offsetX: starting index for x.

While 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 scale every other value in the input strided array starting from the second element,

var Complex128Array = require( '@stdlib/array-complex128' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );

var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var alpha = new Complex128( 2.0, 2.0 );

zscal.ndarray( 2, alpha, x, 2, 1 );
// x => <Complex128Array>[ 1.0, 2.0, -2.0, 14.0, 5.0, 6.0, -2.0, 30.0 ]

Notes

• If N <= 0 , both functions return x unchanged.
• zscal() corresponds to the BLAS level 1 function zscal.

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var Complex128 = require( '@stdlib/complex-float64-ctor' );
var zscal = require( '@stdlib/blas-base-zscal' );

function rand() {
    return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
}

var x = filledarrayBy( 10, 'complex128', rand );
console.log( x.toString() );

var alpha = new Complex128( 2.0, 2.0 );
console.log( alpha.toString() );

// Scales elements from `x` by `alpha`:
zscal( x.length, alpha, x, 1 );
console.log( x.get( x.length-1 ).toString() );

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C APIs

Usage

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

c_zscal( N, alpha, *X, strideX )

Scales values from X by alpha.

#include "stdlib/complex/float64/ctor.h"

double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

c_zscal( 4, alpha, (void *)x, 1 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] stdlib_complex128_t scalar constant.
• X: [inout] void* input array.
• strideX: [in] CBLAS_INT index increment for X.

void c_zscal( const CBLAS_INT N, const stdlib_complex128_t alpha, void *X, const CBLAS_INT strideX );

c_zscal_ndarray( N, alpha, *X, strideX, offsetX )

Scales values from X by alpha using alternative indexing semantics.

#include "stdlib/complex/float64/ctor.h"

double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

c_zscal_ndarray( 4, alpha, (void *)x, 1, 0 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] stdlib_complex128_t scalar constant.
• X: [inout] void* input array.
• strideX: [in] CBLAS_INT index increment for X.
• offsetX: [in] CBLAS_INT starting index for X.

void c_zscal_ndarray( const CBLAS_INT N, const stdlib_complex128_t alpha, void *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/base/zscal.h"
#include "stdlib/complex/float64/ctor.h"
#include <stdio.h>

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

    // Create a complex scalar:
    const stdlib_complex128_t alpha = stdlib_complex128( 2.0, 2.0 );

    // Specify the number of elements:
    const int N = 4;

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

    // Scale the elements of the array:
    c_zscal( N, alpha, (void *)x, strideX );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "x[ %i ] = %lf + %lfj\n", i, x[ i*2 ], x[ (i*2)+1 ] );
    }

    // Scale the elements of the array using alternative indexing semantics:
    c_zscal_ndarray( N, alpha, (void *)x, -strideX, N-1 );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "x[ %i ] = %lf + %lfj\n", i, x[ i*2 ], x[ (i*2)+1 ] );
    }
}

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2025. The Stdlib Authors.