@stdlib/blas-ext-base-dsort2ins

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dsort2ins

Simultaneously sort two double-precision floating-point strided arrays based on the sort order of the first array using insertion sort.

Installation

npm install @stdlib/blas-ext-base-dsort2ins

Usage

var dsort2ins = require( '@stdlib/blas-ext-base-dsort2ins' );

dsort2ins( N, order, x, strideX, y, strideY )

Simultaneously sorts two double-precision floating-point strided arrays based on the sort order of the first array x using insertion sort.

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

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0 ] );
var y = new Float64Array( [ 0.0, 1.0, 2.0, 3.0 ] );

dsort2ins( x.length, 1.0, x, 1, y, 1 );

console.log( x );
// => <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

console.log( y );
// => <Float64Array>[ 3.0, 1.0, 0.0, 2.0 ]

The function has the following parameters:

• N: number of indexed elements.
• order: sort order. If order < 0.0, the input strided array x is sorted in decreasing order. If order > 0.0, the input strided array x is sorted in increasing order. If order == 0.0, the input strided arrays are left unchanged.
• x: first input Float64Array.
• strideX: x index increment.
• y: second input Float64Array.
• strideY: y index increment.

The N and stride parameters determine which elements in x and y are accessed at runtime. For example, to sort every other element

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 ] );
var y = new Float64Array( [ 0.0, 1.0, 2.0, 3.0 ] );
var N = floor( x.length / 2 );

dsort2ins( N, -1.0, x, 2, y, 2 );

console.log( x );
// => <Float64Array>[ 3.0, -2.0, 1.0, -4.0 ]

console.log( y );
// => <Float64Array>[ 2.0, 1.0, 0.0, 3.0 ]

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 ] );
var y0 = new Float64Array( [ 0.0, 1.0, 2.0, 3.0 ] );

// 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*1 ); // start at 2nd element
var N = floor( x0.length/2 );

// Sort every other element...
dsort2ins( N, -1.0, x1, 2, y1, 2 );

console.log( x0 );
// => <Float64Array>[ 1.0, 4.0, 3.0, 2.0 ]

console.log( y0 );
// => <Float64Array>[ 0.0, 3.0, 2.0, 1.0 ]

dsort2ins.ndarray( N, order, x, strideX, offsetX, y, strideY, offsetY )

Simultaneously sorts two double-precision floating-point strided arrays based on the sort order of the first array x using insertion sort and alternative indexing semantics.

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

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0 ] );
var y = new Float64Array( [ 0.0, 1.0, 2.0, 3.0 ] );

dsort2ins.ndarray( x.length, 1.0, x, 1, 0, y, 1, 0 );

console.log( x );
// => <Float64Array>[ -4.0, -2.0, 1.0, 3.0 ]

console.log( y );
// => <Float64Array>[ 3.0, 1.0, 0.0, 2.0 ]

The function has the following additional parameters:

• offsetX: x starting index.
• offsetY: y starting index.

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 access only the last three elements of x

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

var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
var y = new Float64Array( [ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 ] );

dsort2ins.ndarray( 3, 1.0, x, 1, x.length-3, y, 1, y.length-3 );

console.log( x );
// => <Float64Array>[ 1.0, -2.0, 3.0, -6.0, -4.0, 5.0 ]

console.log( y );
// => <Float64Array>[ 0.0, 1.0, 2.0, 5.0, 3.0, 4.0 ]

Notes

• If N <= 0 or order == 0.0, both functions leave x and y unchanged.
• The algorithm distinguishes between -0 and +0. When sorted in increasing order, -0 is sorted before +0. When sorted in decreasing order, -0 is sorted after +0.
• The algorithm sorts NaN values to the end. When sorted in increasing order, NaN values are sorted last. When sorted in decreasing order, NaN values are sorted first.
• The algorithm has space complexity O(1) and worst case time complexity O(N^2).
• The algorithm is efficient for small strided arrays (typically N <= 20) and is particularly efficient for sorting strided arrays which are already substantially sorted.
• The algorithm is stable, meaning that the algorithm does not change the order of strided array elements which are equal or equivalent (e.g., NaN values).
• The input strided arrays are sorted in-place (i.e., the input strided arrays are mutated).

Examples

var round = require( '@stdlib/math-base-special-round' );
var randu = require( '@stdlib/random-base-randu' );
var Float64Array = require( '@stdlib/array-float64' );
var dsort2ins = require( '@stdlib/blas-ext-base-dsort2ins' );

var rand;
var sign;
var x;
var y;
var i;

x = new Float64Array( 10 );
y = new Float64Array( 10 ); // index array
for ( i = 0; i < x.length; i++ ) {
    rand = round( randu()*100.0 );
    sign = randu();
    if ( sign < 0.5 ) {
        sign = -1.0;
    } else {
        sign = 1.0;
    }
    x[ i ] = sign * rand;
    y[ i ] = i;
}
console.log( x );
console.log( y );

dsort2ins( x.length, -1.0, x, -1, y, -1 );
console.log( x );
console.log( y );

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See Also

• @stdlib/blas-ext/base/dsortins: sort a double-precision floating-point strided array using insertion sort.
• @stdlib/blas-ext/base/gsort2ins: simultaneously sort two strided arrays based on the sort order of the first array using insertion sort.
• @stdlib/blas-ext/base/ssort2ins: simultaneously sort two single-precision floating-point strided arrays based on the sort order of the first array using insertion sort.

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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.

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