factory

Return a function which interchanges two vectors.

Usage

var factory = require( '@stdlib/blas/tools/swap-factory' );

factory( base, dtype )

Returns a function which interchanges two vectors.

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

var swap = factory( dswap, 'float64' );

The function has the following parameters:

base: "base" function which interchanges two vectors. Must have an ndarray function signature (i.e., must support index offsets).
dtype: array data type. The function assumes that the data type of all provided arrays is the same.

swap( x, y[, dim] )

Interchanges two vectors.

var Float64Array = require( '@stdlib/array/float64' );
var array = require( '@stdlib/ndarray/array' );
var dswap = require( '@stdlib/blas/base/dswap' ).ndarray;

var swap = factory( dswap, 'float64' );

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 ] ) );

swap( 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 returned function has the following parameters:

x: a non-zero-dimensional ndarray. Must have the same shape as y.
y: a non-zero-dimensional ndarray. 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 dswap = require( '@stdlib/blas/base/dswap' ).ndarray;

var swap = factory( dswap, 'float64' );

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

swap( x, y );

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

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

Notes

For the returned function,

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.

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/base/dswap' ).ndarray;
var factory = require( '@stdlib/blas/tools/swap-factory' );

var swap = factory( dswap, 'float64' );

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 ) );

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