Apply a modified Givens transformation.
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> Apply a modified Givens plane rotation.
``bash`
npm install @stdlib/blas-base-drotm
`javascript`
var drotm = require( '@stdlib/blas-base-drotm' );
#### drotm( N, x, strideX, y, strideY, param )
Applies a modified Givens plane rotation.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );
drotm( 2, x, 2, y, 1, param );
// x =>
// y =>
`
The function has the following parameters:
- N: number of indexed elements.
- x: first input [Float64Array][mdn-float64array].x
- strideX: index increment for .Float64Array
- y: second input [][mdn-float64array].y
- strideY: index increment for .
- 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,
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );
drotm( 3, x, 2, y, 2, param );
// x =>
// y =>
`
Note that indexing is relative to the first index. To introduce an offset, use [typed array][mdn-typed-array] views.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y0 = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 1.0, 0.0, 2.0, 3.0, 0.0 ] );
// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
drotm( 2, x1, 1, y1, 1, param );
// x0 =>
// y0 =>
`
#### drotm.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, param )
Applies a modified Givens plane rotation using alternative indexing semantics.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );
drotm.ndarray( 2, x, 1, 0, y, 2, 1, param );
// x =>
// y =>
`
The function has the following additional parameters:
- offsetX: starting index for x.y
- offsetY: starting index for .
While [typed array][mdn-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,
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var param = new Float64Array( [ 0.0, 0.0, 2.0, -3.0, 0.0 ] );
drotm.ndarray( 3, x, 2, 1, y, 2, 1, param );
// x =>
// y =>
`
- If N <= 0, both functions leave x and y unchanged.drotm()
- corresponds to the [BLAS][blas] level 1 function [drotm][drotm].
`javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var drotm = require( '@stdlib/blas-base-drotm' );
var opts = {
'dtype': 'float64'
};
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:
drotm( x.length, x, 1, y, 1, param );
console.log( x );
console.log( y );
`
*
`c`
#include "stdlib/blas/base/drotm.h"
#### c_drotm( N, \X, strideX, \Y, strideY, param )
Applies a modified Givens plane rotation.
`c
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
double y[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
const double param[5] = { 0.0, 0.0, 2.0, -3.0, 0.0 };
c_drotm( 5, x, 1, y, 1, param );
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[inout] double*
- X: first input array.[in] CBLAS_INT
- strideX: index increment for X.[inout] double*
- Y: second input array.[in] CBLAS_INT
- strideY: index increment for Y.[in] double
- param: parameters for the modified Givens transformation.
`c`
void c_drotm( const CBLAS_INT N, double X, const CBLAS_INT strideX, double Y, const CBLAS_INT strideY, const double *param );
#### c_drotm_ndarray( N, \X, strideX, offsetX, \Y, strideY, offsetY, param )
Applies a modified Givens plane rotation using alternative indexing semantics.
`c
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
double y[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
const double param[5] = { 0.0, 0.0, 2.0, -3.0, 0.0 };
c_drotm_ndarray( 5, x, -1, 4, y, -1, 4, param );
`
The function accepts the following arguments:
- N: [in] CBLAS_INT number of indexed elements.[inout] double*
- X: first input array.[in] CBLAS_INT
- strideX: index increment for X.[in] CBLAS_INT
- offsetX: starting index for X.[inout] double*
- Y: second input array.[in] CBLAS_INT
- strideY: index increment for Y.[in] CBLAS_INT
- offsetY: starting index for Y.[in] double
- param: parameters for the modified Givens transformation.
`c`
void c_drotm_ndarray( const CBLAS_INT N, double X, const CBLAS_INT strideX, const CBLAS_INT offsetX, double Y, const CBLAS_INT strideY, const CBLAS_INT offsetY, const double *param );
`c
#include "stdlib/blas/base/drotm.h"
#include
int main( void ) {
// Create strided arrays:
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0 };
double y[] = { 6.0, 7.0, 8.0, 9.0, 10.0 };
// 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 double param[5] = { 0.0, 0.0, 2.0, -3.0, 0.0 };
// Apply plane rotation:
c_drotm( N, x, strideX, y, strideY, param );
// Print the result:
for ( int i = 0; i < 5; i++ ) {
printf( "x[ %i ] = %lf, y[ %i ] = %lf\n", i, x[ i ], i, y[ i ] );
}
// Apply plane rotation:
c_drotm_ndarray( N, x, -strideX, N-1, y, -strideY, N-1, param );
// Print the result:
for ( int i = 0; i < 5; i++ ) {
printf( "x[ %i ] = %lf, y[ %i ] = %lf\n", i, x[ i ], i, y[ i ] );
}
}
`
*
This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].
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