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dcopyWithin

Perform an in-place copy of elements within a double-precision floating-point array.

Usage

var dcopyWithin = require( '@stdlib/blas/ext/base/dcopy-within' );

dcopyWithin( N, target, start, end, x, strideX )

Performs an in-place copy of elements within a double-precision floating-point array.

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

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

dcopyWithin( x.length, 3, 1, 4, x, 1 );
// x => <Float64Array>[ 1.0, 2.0, 3.0, 2.0, 3.0, 4.0 ]

The function has the following parameters:

  • N: number of indexed elements.
  • target: target index.
  • start: source start index.
  • end: source end index.
  • x: input Float64Array.
  • strideX: stride length.

The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to copy every other element:

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

var x = new Float64Array( [ 1.0, 0.0, 3.0, 0.0, 5.0, 0.0, 7.0, 0.0 ] );

dcopyWithin( 3, 0, 1, 6, x, 2 );
// x => <Float64Array>[ 3.0, 0.0, 5.0, 0.0, 7.0, 0.0, 7.0, 0.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

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

// Initial array...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Copy within the view...
dcopyWithin( 3, 0, 2, 5, x1, 1 );
// x0 => <Float64Array>[ 1.0, 4.0, 5.0, 6.0, 5.0, 6.0, 7.0, 8.0 ]

dcopyWithin.ndarray( N, target, start, end, x, strideX, offsetX )

Performs an in-place copy of elements within a double-precision floating-point array using alternative indexing semantics.

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

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

dcopyWithin.ndarray( x.length, 3, 1, 4, x, 1, 0 );
// x => <Float64Array>[ 1.0, 2.0, 3.0, 2.0, 3.0, 4.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to copy elements starting from the second element:

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

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] );

dcopyWithin.ndarray( 3, 2, 0, 3, x, 1, 2 );
// x => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 3.0, 4.0, 5.0, 8.0 ]

Notes

  • If N <= 0, both functions return the strided array unchanged.
  • If target >= N, both functions return the strided array unchanged.
  • Both functions mutate the provided input strided array.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var dcopyWithin = require( '@stdlib/blas/ext/base/dcopy-within' );

var x = discreteUniform( 10, 0, 500, {
    'dtype': 'float64'
});
console.log( x );

// Copy the first 3 elements to positions 5, 6, 7:
dcopyWithin( 10, 5, 0, 3, x, 1 );
console.log( x );

// Copy elements starting from source index 1 to target index 0:
dcopyWithin( 5, 0, 1, 9, x, 1 );
console.log( x );

C APIs

Usage

#include "stdlib/blas/ext/base/dcopy_within.h"

stdlib_strided_dcopy_within( N, target, start, end, *x, strideX )

Performs an in-place copy of elements within a double-precision floating-point array.

double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

stdlib_strided_dcopy_within( 6, 3, 1, 4, x, 1 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • target: [in] CBLAS_INT target index.
  • start: [in] CBLAS_INT source start index.
  • end: [in] CBLAS_INT source end index.
  • x: [inout] double* input array.
  • strideX: [in] CBLAS_INT stride length.
void stdlib_strided_dcopy_within( const CBLAS_INT N, const CBLAS_INT target, const CBLAS_INT start, const CBLAS_INT end, double *x, const CBLAS_INT strideX );

stdlib_strided_dcopy_within_ndarray( N, target, start, end, *x, strideX, offsetX )

Performs an in-place copy of elements within a double-precision floating-point array using alternative indexing semantics.

double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };

stdlib_strided_dcopy_within_ndarray( 4, 2, 0, 2, x, 1, 1 );

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • target: [in] CBLAS_INT target index.
  • start: [in] CBLAS_INT source start index.
  • end: [in] CBLAS_INT source end index.
  • x: [inout] double* input array.
  • strideX: [in] CBLAS_INT stride length.
  • offsetX: [in] CBLAS_INT starting index.
void stdlib_strided_dcopy_within_ndarray( const CBLAS_INT N, const CBLAS_INT target, const CBLAS_INT start, const CBLAS_INT end, double *x, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/ext/base/dcopy_within.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array:
    double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };

    // Specify the number of elements to copy:
    const int N = 8;

    // Specify a stride:
    const int strideX = 1;

    // Copy elements starting from index 1 to index 4:
    stdlib_strided_dcopy_within( N, 4, 1, 4, x, strideX );

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