srotm

Apply a modified Givens plane rotation.

Installation

npm install @stdlib/blas-base-srotm

Usage

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

srotm( N, x, strideX, y, strideY, param )

Applies a modified Givens plane rotation.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float32Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float32Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

srotm( 2, x, 2, y, 1, param );
// x => <Float32Array>[ ~-17.0, 2.0, ~-18.0, 4.0, 5.0 ]
// y => <Float32Array>[ ~8.0, ~13.0, 8.0, 9.0, 10.0 ]

The function has the following parameters:

• N: number of indexed elements.
• x: first input Float32Array.
• strideX: index increment for x.
• y: second input Float32Array.
• strideY: index increment for y.
• param: parameters for the modified Givens transformation

The N and stride parameters determine how values in the strided arrays are accessed at runtime. For example, to apply a modified Givens plane rotation to every other element,

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float32Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float32Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

srotm( 3, x, 2, y, 2, param );
// x => <Float32Array>[ ~-20.0, 2.0, ~-24.0, 4.0, ~-28.0, 6.0 ]
// y => <Float32Array>[ ~9.0, 8.0, ~15.0, 10.0, ~21.0, 12.0 ]

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

var Float32Array = require( '@stdlib/array-float32' );

// Initial arrays...
var x0 = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y0 = new Float32Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float32Array( [ 1.0, 0.0, 2.0, 3.0, 0.0 ] );

// Create offset views...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float32Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element

srotm( 2, x1, 1, y1, 1, param );
// x0 => <Float32Array>[ 1.0, ~9.0, ~10.0, 4.0, 5.0 ]
// y0 => <Float32Array>[ 6.0, 7.0, 8.0, ~-2.0, ~-3.0 ]

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

Applies a modified Givens plane rotation using alternative indexing semantics.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float32Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float32Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

srotm.ndarray( 2, x, 1, 0, y, 2, 1, param );
// x => <Float32Array>[ ~-20.0, ~-25.0, 3.0, 4.0, 5.0 ]
// y => <Float32Array>[ 6.0, ~9.0, 8.0, ~13.0, 10.0 ]

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

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float32Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float32Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );

srotm.ndarray( 3, x, 2, 1, y, 2, 1, param );
// x => <Float32Array>[ 1.0, ~-22.0, 3.0, ~-26.0, 5.0, ~-30.0 ]
// y => <Float32Array>[ 7.0, ~12.0, 9.0, ~18.0, 11.0, ~24.0 ]

Notes

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

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var srotm = require( '@stdlib/blas-base-srotm' );

var opts = {
    'dtype': 'float32'
};
var x = discreteUniform( 10, 0, 500, opts );
console.log( x );

var y = discreteUniform( x.length, 0, 255, opts );
console.log( y );

var param = discreteUniform( 5, -5, 5, opts );
console.log( param );

// Apply a plane rotation:
srotm( x.length, x, 1, y, 1, param );
console.log( x );
console.log( y );

C APIs

Usage

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

c_srotm( N, *X, strideX, *Y, strideY, param )

Applies a modified Givens plane rotation.

float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
float y[] = { 6.0f, 7.0f, 8.0f, 9.0f, 10.0f };
const float param[5] = { 0.0f, 0.0f, 2.0f, -3.0f, 0.0f };

c_srotm( 5, x, 1, y, 1, param );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• X: [inout] float* first input array.
• strideX: [in] CBLAS_INT index increment for X.
• Y: [inout] float* second input array.
• strideY: [in] CBLAS_INT index increment for Y.
• param: [in] float parameters for the modified Givens transformation.

void c_srotm( const CBLAS_INT N, float *X, const CBLAS_INT strideX, float *Y, const CBLAS_INT strideY, const float *param );

Examples

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

int main( void ) {
    // Create strided arrays:
    float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f };
    float y[] = { 6.0f, 7.0f, 8.0f, 9.0f, 10.0f };

    // Specify the number of elements:
    const int N = 5;

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

    // Specify parameters for the modified Givens transformation:
    const float param[5] = { 0.0f, 0.0f, 2.0f, -3.0f, 0.0f };

    // Apply plane rotation:
    c_srotm( N, x, strideX, y, strideY, param );

    // Print the result:
    for ( int i = 0; i < 5; i++ ) {
        printf( "x[ %i ] = %f, y[ %i ] = %f\n", i, x[ i ], i, y[ i ] );
    }
}

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.

Copyright

Copyright © 2016-2024. The Stdlib Authors.