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zswap

Interchange two complex double-precision floating-point vectors.

This BLAS level 1 routine interchanges complex double-precision floating-point vectors x and y. The operation is performed in-place, with x being overwritten with the values from y, and y being overwritten with the values from x.

Installation

npm install @stdlib/blas-base-zswap

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

zswap( N, x, strideX, y, strideY )

Interchanges two complex double-precision floating-point vectors.

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

var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

zswap( x.length, x, 1, y, 1 );

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

var re = real( z );
// returns 1.0

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

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

re = real( z );
// returns 0.0

im = imag( z );
// returns 0.0

The function has the following parameters:

• N: number of indexed elements.
• x: first input Complex128Array.
• strideX: index increment for x.
• y: second input Complex128Array.
• strideY: index increment for y.

The N and stride parameters determine how values from x are interchanged with values from y. For example, to interchange in reverse order every other value in x into the first N elements of y,

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

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

zswap( 2, x, -2, y, 1 );

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

var re = real( z );
// returns 5.0

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

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

re = real( z );
// returns 0.0

im = imag( z );
// returns 0.0

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

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

// Initial arrays...
var x0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y0 = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex128Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

// Interchange in reverse order every other value from `x1` into `y1`...
zswap( 2, x1, -2, y1, 1 );

var z = y0.get( 2 );
// returns <Complex128>

var re = real( z );
// returns 7.0

var im = imag( z );
// returns 8.0

z = x0.get( 1 );
// returns <Complex128>

re = real( z );
// returns 0.0

im = imag( z );
// returns 0.0

zswap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )

Interchanges two complex double-precision floating-point vectors using alternative indexing semantics.

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

var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

zswap.ndarray( x.length, x, 1, 0, y, 1, 0 );

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

var re = real( z );
// returns 1.0

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

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

re = real( z );
// returns 0.0

im = imag( z );
// returns 0.0

The function has the following additional parameters:

• offsetX: starting index for x.
• offsetY: starting index for y.

While 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 interchange every other value in x starting from the second value into the last N elements in y where x[i] = y[n], x[i+2] = y[n-1], and so on,

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

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

zswap.ndarray( 2, x, 2, 1, y, -1, y.length-1 );

var z = y.get( y.length-1 );
// returns <Complex128>

var re = real( z );
// returns 3.0

var im = imag( z );
// returns 4.0

z = x.get( x.length-1 );
// returns <Complex128>

re = real( z );
// returns 0.0

im = imag( z );
// returns 0.0

Notes

• If N <= 0, both functions leave x and y unchanged.
• zswap() corresponds to the BLAS level 1 function zswap.

Examples

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

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

var x = filledarrayBy( 10, 'complex128', rand );
console.log( x.get( 0 ).toString() );

var y = filledarrayBy( 10, 'complex128', rand );
console.log( y.get( 0 ).toString() );

// Swap elements in `x` into `y` starting from the end of `y`:
zswap( x.length, x, 1, y, -1 );
console.log( x.get( x.length-1 ).toString() );
console.log( y.get( y.length-1 ).toString() );

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C APIs

Usage

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

c_zswap( N, *X, strideX, *Y, strideY )

Interchanges two complex double-precision floating-point vectors.

double x[] = { 1.0, 2.0, 3.0, 4.0 }; // interleaved real and imaginary components
double y[] = { 5.0, 6.0, 7.0, 8.0 };

c_zswap( 2, (void *)x, 1, (void *)y, 1 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• X: [inout] void* first input array.
• strideX: [in] CBLAS_INT index increment for X.
• Y: [inout] void* second input array.
• strideY: [in] CBLAS_INT index increment for Y.

void c_zswap( const CBLAS_INT N, void *X, const CBLAS_INT strideX, void *Y, const CBLAS_INT strideY );

c_zswap_ndarray( N, *X, strideX, offsetX, *Y, strideY, offsetY )

Interchanges two complex double-precision floating-point vectors using alternative indexing semantics.

double x[] = { 1.0, 2.0, 3.0, 4.0 }; // interleaved real and imaginary components
double y[] = { 5.0, 6.0, 7.0, 8.0 };

c_zswap_ndarray( 2, (void *)x, 1, 0, (void *)y, 1, 0 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• X: [inout] void* first input array.
• strideX: [in] CBLAS_INT index increment for X.
• offsetX: [in] CBLAS_INT starting index for X.
• Y: [inout] void* second input array.
• strideY: [in] CBLAS_INT index increment for Y.
• offsetY: [in] CBLAS_INT starting index for Y.

void c_zswap_ndarray( const CBLAS_INT N, void *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, void *Y, const CBLAS_INT strideY, const CBLAS_INT offsetY );

Examples

#include "stdlib/blas/base/zswap.h"
#include <stdio.h>

int main( void ) {
    // Create strided arrays:
    double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
    double y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };

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

    // Specify stride lengths:
    const int strideX = 1;
    const int strideY = -1;

    // Swap elements:
    c_zswap( N, (void *)x, strideX, (void *)y, strideY );

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

    // Swap elements using alternative indexing semantics:
    c_zswap_ndarray( N, (void *)x, -strideX, N-1, (void *)y, strideY, 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 ] );
        printf( "y[ %i ] = %lf + %lfj\n", i, y[ i*2 ], y[ (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 © 2016-2024. The Stdlib Authors.