@stdlib/blas-base-zscal

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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

Usage

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

zscal( N, za, zx, strideX )

Scales values from zx by za.

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

var zx = new Complex128Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );
var za = new Complex128( 2.0, 0.0 );

zscal( 3, za, zx, 1 );

var z = zx.get( 0 );
// returns <Complex128>

var re = real( z );
// returns 2.0

var im = imag( z );
// returns 2.0

The function has the following parameters:

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

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

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

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

zscal( 2, za, zx, 2 );

var z = zx.get( 2 );
// returns <Complex128>

var re = real( z );
// returns 10.0

var im = imag( z );
// returns 12.0

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' );
var real = require( '@stdlib/complex-float64-real' );
var imag = require( '@stdlib/complex-float64-imag' );

// Initial array:
var zx0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

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

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

// Scales every other value from `zx1` by `za`...
zscal( 3, za, zx1, 1 );

var z = zx0.get( 1 );
// returns <Complex128>

var re = real( z );
// returns -2.0

var im = imag( z );
// returns 14.0

zscal.ndarray( N, za, zx, strideX, offsetX )

Scales values from zx by za using alternative indexing semantics.

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

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

zscal.ndarray( 3, za, zx, 1, 0 );

var z = zx.get( 0 );
// returns <Complex128>

var re = real( z );
// returns -2.0

var im = imag( z );
// returns 6.0

The function has the following additional parameters:

• offsetX: starting index for zx.

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 real = require( '@stdlib/complex-float64-real' );
var imag = require( '@stdlib/complex-float64-imag' );

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

zscal.ndarray( 2, za, zx, 2, 1 );

var z = zx.get( 3 );
// returns <Complex128>

var re = real( z );
// returns -2.0

var im = imag( z );
// returns 30.0

Notes

• If N <= 0 or strideX <= 0 , both functions return zx 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 zx = filledarrayBy( 10, 'complex128', rand );
console.log( zx.toString() );

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

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

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C APIs

Usage

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

c_zscal( N, za, *ZX, strideX )

Scales values from ZX by za.

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

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

c_zscal( 4, za, (void *)zx, 1 );

The function accepts the following arguments:

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

void c_zscal( const CBLAS_INT N, const stdlib_complex128_t za, void *ZX, const CBLAS_INT strideX );

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

    // Create a complex scalar:
    const stdlib_complex128_t ca = 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, za, (void *)zx, strideX );

    // Print the result:
    for ( int i = 0; i < N; i++ ) {
        printf( "zx[ %i ] = %f + %fj\n", i, zx[ i*2 ], zx[ (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

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