@stdlib/blas-base-cswap
v0.3.0
Published
Interchanges two complex single-precision floating-point vectors.
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cswap
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-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );
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 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
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 realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );
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( 2, 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-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );
// 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-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );
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 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]
,...,
var Complex64Array = require( '@stdlib/array-complex64' );
var realf = require( '@stdlib/complex-float32-real' );
var imagf = require( '@stdlib/complex-float32-imag' );
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 leavex
andy
unchanged. cswap()
corresponds to the BLAS level 1 functioncswap
.
Examples
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var Complex64 = require( '@stdlib/complex-float32-ctor' );
var cswap = require( '@stdlib/blas-base-cswap' );
function rand() {
return new Complex64( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
}
var x = filledarrayBy( 10, 'complex64', rand );
console.log( x.get( 0 ).toString() );
var y = filledarrayBy( 10, 'complex64', rand );
console.log( y.get( 0 ).toString() );
// Swap elements in `x` into `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() );
C APIs
Usage
#include "stdlib/blas/base/cswap.h"
c_cswap( N, *X, strideX, *Y, strideY )
Interchanges two complex single-precision floating-point vectors.
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_cswap( 2, (void *)x, 1, (void *)Y, 1 );
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 forX
. - Y:
[inout] void*
first input array. - strideY:
[in] CBLAS_INT
index increment forY
.
void c_cswap( const CBLAS_INT N, void *X, const CBLAS_INT strideX, void *Y, const CBLAS_INT strideY );
Examples
#include "stdlib/blas/base/cswap.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;
// Copy elements:
c_cswap( N, (void *)x, strideX, (void *)y, strideY );
// 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 ] );
}
}
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.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.