zswap
Interchange two complex double-precision floating-point vectors.
This BLAS level 1 routine interchanges complex double-precision floating-point vectors x and y. The operation is performed in-place, with x being overwritten with the values from y, and y being overwritten with the values from x.
Usage
var zswap = require( '@stdlib/blas/base/zswap' );
zswap( N, x, strideX, y, strideY )
Interchanges two complex double-precision floating-point vectors.
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
zswap( x.length, x, 1, y, 1 );
var z = y.get( 0 );
// returns <Complex128>
var re = real( z );
// returns 1.0
var im = imag( z );
// returns 2.0
z = x.get( 0 );
// returns <Complex128>
re = real( z );
// returns 0.0
im = imag( z );
// returns 0.0
The function has the following parameters:
- N: number of indexed elements.
- x: first input
Complex128Array. - strideX: index increment for
x. - y: second input
Complex128Array. - 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 Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
zswap( 2, x, -2, y, 1 );
var z = y.get( 0 );
// returns <Complex128>
var re = real( z );
// returns 5.0
var im = imag( z );
// returns 6.0
z = x.get( 0 );
// returns <Complex128>
re = real( z );
// returns 0.0
im = imag( z );
// returns 0.0
Note that indexing is relative to the first index. To introduce an offset, use typed array views.
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
// Initial arrays...
var x0 = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y0 = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
// Create offset views...
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex128Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element
// Interchange in reverse order every other value from `x1` into `y1`...
zswap( 2, x1, -2, y1, 1 );
var z = y0.get( 2 );
// returns <Complex128>
var re = real( z );
// returns 7.0
var im = imag( z );
// returns 8.0
z = x0.get( 1 );
// returns <Complex128>
re = real( z );
// returns 0.0
im = imag( z );
// returns 0.0
zswap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )
Interchanges two complex double-precision floating-point vectors using alternative indexing semantics.
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
zswap.ndarray( x.length, x, 1, 0, y, 1, 0 );
var z = y.get( 0 );
// returns <Complex128>
var re = real( z );
// returns 1.0
var im = imag( z );
// returns 2.0
z = x.get( 0 );
// returns <Complex128>
re = real( z );
// returns 0.0
im = imag( 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], and so on,
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var x = new Complex128Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );
var y = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
zswap.ndarray( 2, x, 2, 1, y, -1, y.length-1 );
var z = y.get( y.length-1 );
// returns <Complex128>
var re = real( z );
// returns 3.0
var im = imag( z );
// returns 4.0
z = x.get( x.length-1 );
// returns <Complex128>
re = real( z );
// returns 0.0
im = imag( z );
// returns 0.0
Notes
Examples
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var Complex128 = require( '@stdlib/complex/float64/ctor' );
var zswap = require( '@stdlib/blas/base/zswap' );
function rand() {
return new Complex128( discreteUniform( 0, 10 ), discreteUniform( -5, 5 ) );
}
var x = filledarrayBy( 10, 'complex128', rand );
console.log( x.get( 0 ).toString() );
var y = filledarrayBy( 10, 'complex128', rand );
console.log( y.get( 0 ).toString() );
// Swap elements in `x` into `y` starting from the end of `y`:
zswap( 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/zswap.h"
c_zswap( N, *X, strideX, *Y, strideY )
Interchanges two complex double-precision floating-point vectors.
double x[] = { 1.0, 2.0, 3.0, 4.0 }; // interleaved real and imaginary components
double y[] = { 5.0, 6.0, 7.0, 8.0 };
c_zswap( 2, (void *)x, 1, (void *)y, 1 );
The function accepts the following arguments:
- N:
[in] CBLAS_INTnumber of indexed elements. - X:
[inout] void*first input array. - strideX:
[in] CBLAS_INTindex increment forX. - Y:
[inout] void*second input array. - strideY:
[in] CBLAS_INTindex increment forY.
void c_zswap( const CBLAS_INT N, void *X, const CBLAS_INT strideX, void *Y, const CBLAS_INT strideY );
c_zswap_ndarray( N, *X, strideX, offsetX, *Y, strideY, offsetY )
Interchanges two complex double-precision floating-point vectors using alternative indexing semantics.
double x[] = { 1.0, 2.0, 3.0, 4.0 }; // interleaved real and imaginary components
double y[] = { 5.0, 6.0, 7.0, 8.0 };
c_zswap_ndarray( 2, (void *)x, 1, 0, (void *)y, 1, 0 );
The function accepts the following arguments:
- N:
[in] CBLAS_INTnumber of indexed elements. - X:
[inout] void*first input array. - strideX:
[in] CBLAS_INTindex increment forX. - offsetX:
[in] CBLAS_INTstarting index forX. - Y:
[inout] void*second input array. - strideY:
[in] CBLAS_INTindex increment forY. - offsetY:
[in] CBLAS_INTstarting index forY.
void c_zswap_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 );
Examples
#include "stdlib/blas/base/zswap.h"
#include <stdio.h>
int main( void ) {
// Create strided arrays:
double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };
double y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
// Specify the number of elements:
const int N = 4;
// Specify stride lengths:
const int strideX = 1;
const int strideY = -1;
// Swap elements:
c_zswap( N, (void *)x, strideX, (void *)y, strideY );
// Print the result:
for ( int i = 0; i < N; i++ ) {
printf( "x[ %i ] = %lf + %lfj\n", i, x[ i*2 ], x[ (i*2)+1 ] );
printf( "y[ %i ] = %lf + %lfj\n", i, y[ i*2 ], y[ (i*2)+1 ] );
}
// Swap elements using alternative indexing semantics:
c_zswap_ndarray( N, (void *)x, -strideX, N-1, (void *)y, strideY, N-1 );
// Print the result:
for ( int i = 0; i < N; i++ ) {
printf( "x[ %i ] = %lf + %lfj\n", i, x[ i*2 ], x[ (i*2)+1 ] );
printf( "y[ %i ] = %lf + %lfj\n", i, y[ i*2 ], y[ (i*2)+1 ] );
}
}