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    @stdlib/blas-base-dcopy
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    0.0.8 • Public • Published

    dcopy

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    Copy values from x into y.

    Installation

    npm install @stdlib/blas-base-dcopy

    Usage

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

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

    Copies values from x into y.

    var Float64Array = require( '@stdlib/array-float64' );
    
    var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
    var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
    
    dcopy( x.length, x, 1, y, 1 );
    // y => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]

    The function has the following parameters:

    • N: number of values to copy.
    • x: input Float64Array.
    • strideX: index increment for x.
    • y: destination Float64Array.
    • 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 Float64Array = require( '@stdlib/array-float64' );
    var floor = require( '@stdlib/math-base-special-floor' );
    
    var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
    var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
    
    var N = floor( x.length / 2 );
    
    dcopy( N, x, -2, y, 1 );
    // y => <Float64Array>[ 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`...
    dcopy( N, x1, -2, y1, 1 );
    // y0 => <Float64Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

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

    Copies values from x into y using alternative indexing semantics.

    var Float64Array = require( '@stdlib/array-float64' );
    
    var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0 ] );
    var y = new Float64Array( [ 6.0, 7.0, 8.0, 9.0, 10.0 ] );
    
    dcopy.ndarray( x.length, x, 1, 0, y, 1, 0 );
    // y => <Float64Array>[ 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 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 Float64Array = require( '@stdlib/array-float64' );
    var floor = require( '@stdlib/math-base-special-floor' );
    
    var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
    var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
    
    var N = floor( x.length / 2 );
    
    dcopy.ndarray( N, x, 2, 1, y, -1, y.length-1 );
    // y => <Float64Array>[ 7.0, 8.0, 9.0, 6.0, 4.0, 2.0 ]

    Notes

    • If N <= 0, both functions return y unchanged.
    • dcopy() corresponds to the BLAS level 1 function dcopy.

    Examples

    var randu = require( '@stdlib/random-base-randu' );
    var round = require( '@stdlib/math-base-special-round' );
    var Float64Array = require( '@stdlib/array-float64' );
    var dcopy = require( '@stdlib/blas-base-dcopy' );
    
    var x;
    var y;
    var i;
    
    x = new Float64Array( 10 );
    y = new Float64Array( 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`:
    dcopy( x.length, x, 1, y, -1 );
    console.log( y );

    See Also


    Notice

    This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

    For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

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    License

    See LICENSE.

    Copyright

    Copyright © 2016-2022. The Stdlib Authors.

    Install

    npm i @stdlib/blas-base-dcopy

    Homepage

    stdlib.io

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