csrot

Apply a plane rotation.

Installation

npm install @stdlib/blas-base-csrot

Usage

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

csrot( N, x, strideX, y, strideY, c, s )

Applies a plane rotation.

var Complex64Array = require( '@stdlib/array-complex64' );

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 ] );

csrot( x.length, x, 1, y, 1, 0.8, 0.6 );
// x => <Complex64Array>[ ~0.8, ~1.6, ~2.4, ~3.2, 4.0, ~4.8, ~5.6, ~6.4 ]
// y => <Complex64Array>[ ~-0.6, ~-1.2, ~-1.8, ~-2.4, -3.0, ~-3.6, ~-4.2, ~-4.8 ]

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 and y are accessed at runtime. For example, to apply a plane rotation to every other element,

var Complex64Array = require( '@stdlib/array-complex64' );

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 ] );

csrot( 2, x, 2, y, 2, 0.8, 0.6 );
// x => <Complex64Array>[ ~0.8, ~1.6, 3.0, 4.0, 4.0, ~4.8, 7.0, 8.0 ]
// y => <Complex64Array>[ ~-0.6, ~-1.2, 0.0, 0.0, -3.0, ~-3.6, 0.0, 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' );

// 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

csrot( 2, x1, -2, y1, 1, 0.8, 0.6 );
// x0 => <Complex64Array>[ 1.0, 2.0, ~2.4, ~3.2, 5.0, 6.0, ~5.6, ~6.4 ]
// y0 => <Complex64Array>[ 0.0, 0.0, 0.0, 0.0, ~-4.2, ~-4.8, ~-1.8, ~-2.4 ]

csrot.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, c, s )

Applies a plane rotation using alternative indexing semantics.

var Complex64Array = require( '@stdlib/array-complex64' );

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 ] );

csrot.ndarray( x.length, x, 1, 0, y, 1, 0, 0.8, 0.6 );
// x => <Complex64Array>[ ~0.8, ~1.6, ~2.4, ~3.2, 4.0, ~4.8 ]
// y => <Complex64Array>[ ~-0.6, ~-1.2, ~-1.8, ~-2.4, -3.0, ~-3.6 ]

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 apply a plane rotation to every other element starting from the second element,

var Complex64Array = require( '@stdlib/array-complex64' );

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 ] );

csrot.ndarray( 2, x, 2, 1, y, 2, 1, 0.8, 0.6 );
// x => <Complex64Array>[ 1.0, 2.0, ~2.4, ~3.2, 5.0, 6.0, ~5.6, ~6.4 ]
// y => <Complex64Array>[ 0.0, 0.0, ~-1.8, ~-2.4, 0.0, 0.0, ~-4.2, ~-4.8 ]

Notes

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

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );
var ccopy = require( '@stdlib/blas-base-ccopy' );
var zeros = require( '@stdlib/array-zeros' );
var logEach = require( '@stdlib/console-log-each' );
var csrot = require( '@stdlib/blas-base-csrot' );

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

// Generate random input arrays:
var x = filledarrayBy( 10, 'complex64', rand );
var xc = ccopy( x.length, x, 1, zeros( x.length, 'complex64' ), 1 );

var y = filledarrayBy( 10, 'complex64', rand );
var yc = ccopy( y.length, y, 1, zeros( y.length, 'complex64' ), 1 );

// Apply a plane rotation:
csrot( x.length, x, 1, y, 1, 0.8, 0.6 );

// Print the results:
logEach( '(%s,%s) => (%s,%s)', xc, yc, x, y );

C APIs

Usage

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

c_csrot( N, *X, strideX, *Y, strideY, c, s )

Applies a plane rotation.

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_csrot( 2, (void *)x, 1, (void *)y, 1, 0.8f, 0.6f );

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.
• c: [in] float cosine of the angle of rotation.
• s: [in] float sine of the angle of rotation.

void c_csrot( const CBLAS_INT N, void *X, const CBLAS_INT strideX, void *Y, const CBLAS_INT strideY, const float c, const float s );

c_csrot_ndarray( N, *X, strideX, offsetX, *Y, strideY, offsetY, c, s )

Applies a plane rotation using alternative indexing semantics.

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_csrot_ndarray( 2, (void *)x, 1, 0, (void *)y, 1, 0, 0.8f, 0.6f );

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.
• c: [in] float cosine of the angle of rotation.
• s: [in] float sine of the angle of rotation.

void c_csrot_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, const float c, const float s );

Examples

#include "stdlib/blas/base/csrot.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;

    // Apply a plane rotation:
    c_csrot( N, (void *)x, strideX, (void *)y, strideY, 0.8f, 0.6f );

    // 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 ] );
    }
}

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 © 2016-2026. The Stdlib Authors.