zdscal

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

Installation

npm install @stdlib/blas-base-zdscal

Usage

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

zdscal( N, alpha, x, strideX )

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

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

var x = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );

zdscal( 3, 2.0, 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 constant.
• x: input Complex128Array.
• strideX: stride length for x.

The N and stride parameters determine which elements in x are scaled by alpha. For example, to scale every other element in x by alpha,

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

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

zdscal( 2, 2.0, 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' );

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

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

// Scale every element in `x1`:
zdscal( 3, 2.0, x1, 1 );
// x0 => <Complex128Array>[ 1.0, 2.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0 ]

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

Scales a double-precision complex floating-point vector by a double-precision floating-point constant using alternative indexing semantics.

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

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

zdscal.ndarray( 3, 2.0, x, 1, 0 );
// x => <Complex128Array>[ 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 ]

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 element in the input strided array starting from the second element,

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

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

zdscal.ndarray( 2, 2.0, x, 2, 1 );
// x => <Complex128Array>[ 1.0, 2.0, 6.0, 8.0, 5.0, 6.0, 14.0, 16.0 ]

Notes

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

Examples

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

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

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

zdscal( x.length, 2.0, x, 1 );
console.log( x.toString() );

C APIs

Usage

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

c_zdscal( N, alpha, *X, strideX )

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

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

stdlib_complex128_t x[] = {
    stdlib_complex128( 1.0, 2.0 ),
    stdlib_complex128( 3.0, 4.0 ),
    stdlib_complex128( 5.0, 6.0 )
};

c_zdscal( 3, 2.0, x, 1 );

The function accepts the following arguments:

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

void c_zdscal( const CBLAS_INT N, const double alpha, void *X, const CBLAS_INT strideX );

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

Scales a double-precision complex floating-point vector by a double-precision floating-point constant using alternative indexing semantics.

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

stdlib_complex128_t x[] = {
    stdlib_complex128( 1.0, 2.0 ),
    stdlib_complex128( 3.0, 4.0 ),
    stdlib_complex128( 5.0, 6.0 )
};

c_zdscal_ndarray( 3, 2.0, x, 1, 0 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• alpha: [in] double 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_zdscal_ndarray( const CBLAS_INT N, const double alpha, void *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/base/zdscal.h"
#include "stdlib/complex/float64/ctor.h"
#include "stdlib/complex/float64/real.h"
#include "stdlib/complex/float64/imag.h"
#include <stdio.h>

int main( void ) {
    stdlib_complex128_t x[] = {
        stdlib_complex128( 1.0, 2.0 ),
        stdlib_complex128( 3.0, 4.0 ),
        stdlib_complex128( 5.0, 6.0 ),
        stdlib_complex128( 7.0, 8.0 )
    };

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

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

    c_zdscal( N, 2.0, (void *)x, strideX );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "x[ %i ] = %lf + %lfj\n", i, stdlib_complex128_real( x[ i ] ), stdlib_complex128_imag( x[ i ] ) );
    }

    c_zdscal_ndarray( N, 2.0, (void *)x, strideX, 0 );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "x[ %i ] = %lf + %lfj\n", i, stdlib_complex128_real( x[ i ] ), stdlib_complex128_imag( x[ i ] ) );
    }
}

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.

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License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.