@stdlib/blas-base-zswap NPM

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

Usage

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

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

Interchange two complex double-precision floating-point vectors.

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

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

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

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

License

See LICENSE.

@stdlib/blas-base-zswap v0.1.0