sswap

Interchange two single-precision floating-point vectors.

Usage

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

sswap( N, x, strideX, y, strideY )

Interchanges vectors x and y.

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 ] );

sswap( x.length, x, 1, y, 1 );
// x => <Float32Array>[ 6.0, 7.0, 8.0, 9.0, 10.0 ]
// y => <Float32Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]

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.

The N and stride parameters determine how values from the strided arrays are accessed at runtime. For example, to swap in reverse order every other value in x with the first N elements of y,

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 ] );

sswap( 3, x, -2, y, 1 );
// x => <Float32Array>[ 9.0, 2.0, 8.0, 4.0, 7.0, 6.0 ]
// y => <Float32Array>[ 5.0, 3.0, 1.0, 10.0, 11.0, 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, 6.0 ] );
var y0 = new Float32Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

// 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

// Swap in reverse order every other value from `x1` with `y1`...
sswap( 3, x1, -2, y1, 1 );
// x0 => <Float32Array>[ 1.0, 12.0, 3.0, 11.0, 5.0, 10.0 ]
// y0 => <Float32Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

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

Interchanges vectors x and y 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 ] );

sswap.ndarray( x.length, x, 1, 0, y, 1, 0 );
// x => <Float32Array>[ 6.0, 7.0, 8.0, 9.0, 10.0 ]
// y => <Float32Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]

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 swap every other value in x starting from the second value with the last N elements in y where x[i] = y[n], x[i+2] = y[n-1],...,

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 ] );

sswap.ndarray( 3, x, 2, 1, y, -1, y.length-1 );
// x => <Float32Array>[ 1.0, 12.0, 3.0, 11.0, 5.0, 10.0 ]
// y => <Float32Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

Notes

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

Examples

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

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 );

// Swap elements in `x` and `y` starting from the end of `y`:
sswap( x.length, x, 1, y, -1 );
console.log( x );
console.log( y );

C APIs

Usage

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

c_sswap( N, *X, strideX, *Y, strideY )

Interchanges two single-precision floating-point vectors.

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

c_sswap( 5, x, 1, y, 1 );

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.
void c_sswap( const CBLAS_INT N, float *X, const CBLAS_INT strideX, float *Y, const CBLAS_INT strideY );

c_sswap_ndarray( N, *X, strideX, offsetX, *Y, strideY, offsetY )

Interchanges two single-precision floating-point vectors using alternative indexing semantics.

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

c_sswap_ndarray( 3, x, 1, 2, y, 1, 2 );

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.
  • offsetX: [in] CBLAS_INT starting index for X.
  • Y: [inout] float* second input array.
  • strideY: [in] CBLAS_INT index increment for Y.
  • offsetY: [in] CBLAS_INT starting index for Y.
void c_sswap_ndarray( const CBLAS_INT N, float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, float *Y, const CBLAS_INT strideY, CBLAS_INT offsetY );

Examples

#include "stdlib/blas/base/sswap.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 indexed elements:
    const int N = 4;

    // Specify stride lengths:
    const int strideX = 2;
    const int strideY = -2;

    // Interchange elements:
    c_sswap( N, x, strideX, y, strideY );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "x[ %i ] = %f\n", i, x[ i ] );
        printf( "y[ %i ] = %f\n", i, y[ i ] );
    }

    // Interchange elements:
    c_sswap_ndarray( N, x, strideX, 0, y, strideY, 6 );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "x[ %i ] = %f\n", i, x[ i ] );
        printf( "y[ %i ] = %f\n", i, y[ i ] );
    }
}

See Also

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