gcopy

Copy values from x into y.

Usage

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

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

Copies values from x into y.

var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ];

gcopy( x.length, x, 1, y, 1 );
// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]

The function accepts the following parameters:

  • N: number of values to copy.
  • x: input Array or typed array.
  • strideX: index increment for x.
  • y: destination array or typed array.
  • strideY: index increment for y.

The N and stride parameters determine how values from x are copied into y. For example, to copy in reverse order every other value in x into the first N elements of y,

var floor = require( '@stdlib/math/base/special/floor' );

var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ];

var N = floor( x.length / 2 );

gcopy( N, x, -2, y, 1 );
// y => [ 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 Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element

var N = floor( x0.length / 2 );

// Copy in reverse order every other value from `x1` into `y1`...
gcopy( N, x1, -2, y1, 1 );
// y0 => <Float64Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

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

Copies values from x into y, with alternative indexing semantics.

var x = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var y = [ 6.0, 7.0, 8.0, 9.0, 10.0 ];

gcopy.ndarray( x.length, x, 1, 0, y, 1, 0 );
// y => [ 1.0, 2.0, 3.0, 4.0, 5.0 ]

The function accepts 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 offsetX and offsetY parameters support indexing semantics based on starting indices. For example, to copy 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 floor = require( '@stdlib/math/base/special/floor' );

var x = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ];
var y = [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ];

var N = floor( x.length / 2 );

gcopy.ndarray( N, x, 2, 1, y, -1, y.length-1 );
// y => [ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

Notes

  • If N <= 0, both functions return y unchanged.
  • gcopy() corresponds to the BLAS level 1 function dcopy with the exception that this implementation works with any array type, not just Float64Arrays. Depending on the environment, the typed versions (dcopy, scopy, etc.) are likely to be significantly more performant.

Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var Float64Array = require( '@stdlib/array/float64' );
var Uint8ClampedArray = require( '@stdlib/array/uint8c' );
var gcopy = require( '@stdlib/blas/base/gcopy' );

var x;
var y;
var i;

x = new Float64Array( 10 );
y = new Uint8ClampedArray( 10 );
for ( i = 0; i < x.length; i++ ) {
    x[ i ] = round( randu()*500.0 );
    y[ i ] = round( randu()*255.0 );
}
console.log( x );
console.log( y );

// Copy elements from `x` into `y` starting from the end of `y`:
gcopy( x.length, x, 1, y, -1 );
console.log( y );