dswap

Interchange two double-precision floating-point vectors.

Usage

var dswap = require( '@stdlib/blas/dswap' );

dswap( x, y[, dim] )

Interchanges two double-precision floating-point vectors x and y.

var Float64Array = require( '@stdlib/array/float64' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0 ] ) );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0 ] ) );

dswap( x, y );

var xbuf = x.data;
// returns <Float64Array>[ 2.0, 6.0, -1.0, -4.0, 8.0 ]

var ybuf = y.data;
// returns <Float64Array>[ 4.0, 2.0, -3.0, 5.0, -1.0 ]

The function has the following parameters:

  • x: a non-zero-dimensional ndarray whose underlying data type is float64. Must have the same shape as y.
  • y: a non-zero-dimensional ndarray whose underlying data type is float64. Must have the same shape as x.
  • dim: dimension along which to interchange vectors. Must be a negative integer. Negative indices are resolved relative to the last array dimension, with the last dimension corresponding to -1. Default: -1.

For multi-dimensional input ndarrays, the function performs batched computation, such that the function interchanges each pair of vectors in x and y according to the specified dimension index.

var Float64Array = require( '@stdlib/array/float64' );
var array = require( '@stdlib/ndarray/array' );

var opts = {
    'shape': [ 2, 3 ]
};
var x = array( new Float64Array( [ 4.0, 2.0, -3.0, 5.0, -1.0, 3.0 ] ), opts );
var y = array( new Float64Array( [ 2.0, 6.0, -1.0, -4.0, 8.0, 2.0 ] ), opts );

var v1 = x.get( 0, 0 );
// returns 4.0

var v2 = y.get( 0, 0 );
// returns 2.0

dswap( x, y );

v1 = x.get( 0, 0 );
// returns 2.0

v2 = y.get( 0, 0 );
// returns 4.0

Notes

  • Both input ndarrays must have the same shape.
  • Negative indices are resolved relative to the last ndarray dimension, with the last dimension corresponding to -1.
  • For multi-dimensional ndarrays, batched computation effectively means swapping all of x with all of y; however, the choice of dim will significantly affect performance. For best performance, specify a dim which best aligns with the memory layout of provided ndarrays.
  • dswap() provides a higher-level interface to the BLAS level 1 function dswap.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var array = require( '@stdlib/ndarray/array' );
var dswap = require( '@stdlib/blas/dswap' );

var opts = {
    'dtype': 'float64'
};

var x = array( discreteUniform( 10, 0, 100, opts ), {
    'shape': [ 5, 2 ]
});
console.log( ndarray2array( x ) );

var y = array( discreteUniform( 10, 0, 10, opts ), {
    'shape': x.shape
});
console.log( ndarray2array( y ) );

dswap( x, y );
console.log( ndarray2array( x ) );
console.log( ndarray2array( y ) );

See Also

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