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cswap

Interchange two complex single-precision floating-point vectors.

Installation

npm install @stdlib/blas-base-cswap

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

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

Interchanges two complex single-precision floating-point vectors.

var Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

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

var z = y.get( 0 );
// returns <Complex64>

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

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

z = x.get( 0 );
// returns <Complex64>

re = realf( z );
// returns 0.0

im = imagf( z );
// returns 0.0

The function has the following parameters:

• N: number of indexed elements.
• x: first input Complex64Array.
• strideX: index increment for x.
• y: second input Complex64Array.
• 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 Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

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

var z = y.get( 0 );
// returns <Complex64>

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

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

z = x.get( 0 );
// returns <Complex64>

re = realf( z );
// returns 0.0

im = imagf( z );
// returns 0.0

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

var Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );

// Initial arrays...
var x0 = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y0 = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Complex64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex64Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element

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

var z = y0.get( 2 );
// returns <Complex64>

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

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

z = x0.get( 1 );
// returns <Complex64>

re = realf( z );
// returns 0.0

im = imagf( z );
// returns 0.0

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

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

var Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

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

var z = y.get( 0 );
// returns <Complex64>

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

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

z = x.get( 0 );
// returns <Complex64>

re = realf( z );
// returns 0.0

im = imagf( 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],...,

var Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );

var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y = new Complex64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

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

var z = y.get( y.length-1 );
// returns <Complex64>

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

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

z = x.get( x.length-1 );
// returns <Complex64>

re = realf( z );
// returns 0.0

im = imagf( z );
// returns 0.0

Notes

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

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );
var cswap = require( '@stdlib/blas-base-cswap' );

function rand() {
    return new Complex64( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
}

var x = filledarrayBy( 10, 'complex64', rand );
console.log( x.get( 0 ).toString() );

var y = filledarrayBy( 10, 'complex64', rand );
console.log( y.get( 0 ).toString() );

// Swap elements in `x` into `y` starting from the end of `y`:
cswap( 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/cswap.h"

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

Interchanges two complex single-precision floating-point vectors.

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

c_cswap( 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* first input array.
• strideY: [in] CBLAS_INT index increment for Y.

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

Examples

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

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

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

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

    // Copy elements:
    c_cswap( N, (void *)x, strideX, (void *)y, strideY );

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

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See Also

• @stdlib/blas-base/ccopy: copy values from one complex single-precision floating-point vector to another complex single-precision floating-point vector.

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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.