@stdlib/blas-base-cswap
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    0.0.6 • Public • Published

    cswap

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    Interchange two complex single-precision floating-point vectors.

    Installation

    npm install @stdlib/blas-base-cswap

    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-realf' );
    var imagf = require( '@stdlib/complex-imagf' );
    
    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 values to swap.
    • x: input Complex64Array.
    • strideX: index increment for x.
    • y: destination 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 floor = require( '@stdlib/math-base-special-floor' );
    var realf = require( '@stdlib/complex-realf' );
    var imagf = require( '@stdlib/complex-imagf' );
    
    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 ] );
    
    var N = floor( x.length / 2 );
    
    cswap( N, 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-realf' );
    var imagf = require( '@stdlib/complex-imagf' );
    
    // 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-realf' );
    var imagf = require( '@stdlib/complex-imagf' );
    
    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 offsetX and offsetY 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-realf' );
    var imagf = require( '@stdlib/complex-imagf' );
    
    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 Complex64Array = require( '@stdlib/array-complex64' );
    var cswap = require( '@stdlib/blas-base-cswap' );
    
    var re = discreteUniform.factory( 0, 10 );
    var im = discreteUniform.factory( -5, 5 );
    
    var x = new Complex64Array( 10 );
    var y = new Complex64Array( 10 );
    
    var i;
    for ( i = 0; i < x.length; i++ ) {
        x.set( [ re(), im() ], i );
        y.set( [ re(), im() ], i );
    }
    console.log( x.get( 0 ).toString() );
    console.log( y.get( 0 ).toString() );
    
    // Swap elements in `x` and `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() );

    See Also

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

    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 © 2016-2022. The Stdlib Authors.

    Install

    npm i @stdlib/blas-base-cswap

    Homepage

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    Version

    0.0.6

    License

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    Total Files

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