gsort2sh

Simultaneously sort two strided arrays based on the sort order of the first array using Shellsort.

Installation

npm install @stdlib/blas-ext-base-gsort2sh

Usage

var gsort2sh = require( '@stdlib/blas-ext-base-gsort2sh' );

gsort2sh( N, order, x, strideX, y, strideY )

Simultaneously sorts two strided arrays based on the sort order of the first array using Shellsort.

var x = [ 1.0, -2.0, 3.0, -4.0 ];
var y = [ 0.0, 1.0, 2.0, 3.0 ];

gsort2sh( x.length, 1.0, x, 1, y, 1 );

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

console.log( y );
// => [ 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 Array or typed array.
• strideX: stride length for x.
• y: second input Array or typed array.
• strideY: stride length for y.

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

var x = [ 1.0, -2.0, 3.0, -4.0 ];
var y = [ 0.0, 1.0, 2.0, 3.0 ];

gsort2sh( 2, -1.0, x, 2, y, 2 );

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

console.log( y );
// => [ 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' );

// 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

// Sort every other element...
gsort2sh( 2, -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 ]

gsort2sh.ndarray( N, order, x, strideX, offsetX, y, strideY, offsetY )

Simultaneously sorts two strided arrays based on the sort order of the first array using Shellsort and alternative indexing semantics.

var x = [ 1.0, -2.0, 3.0, -4.0 ];
var y = [ 0.0, 1.0, 2.0, 3.0 ];

gsort2sh.ndarray( x.length, 1.0, x, 1, 0, y, 1, 0 );

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

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

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 offset parameters support indexing semantics based on starting indices. For example, to access only the last three elements:

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

gsort2sh.ndarray( 3, 1.0, x, 1, x.length-3, y, 1, y.length-3 );

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

console.log( y );
// => [ 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.
• Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array-base/accessor).
• 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^(4/3)).
• The algorithm is efficient for shorter strided arrays (typically N <= 50).
• The algorithm is unstable, meaning that the algorithm may 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).
• Depending on the environment, the typed versions (dsort2sh, ssort2sh, etc.) are likely to be significantly more performant.

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var gsort2sh = require( '@stdlib/blas-ext-base-gsort2sh' );

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'float64'
});
var y = discreteUniform( 10, -100, 100, {
    'dtype': 'float64'
});
console.log( x );
console.log( y );

gsort2sh( x.length, -1.0, x, -1, y, -1 );
console.log( x );
console.log( y );

References

• Shell, Donald L. 1959. "A High-Speed Sorting Procedure." Communications of the ACM 2 (7). Association for Computing Machinery: 30–32. doi:10.1145/368370.368387.
• Sedgewick, Robert. 1986. "A new upper bound for Shellsort." Journal of Algorithms 7 (2): 159–73. doi:10.1016/0196-6774(86)90001-5.
• Ciura, Marcin. 2001. "Best Increments for the Average Case of Shellsort." In Fundamentals of Computation Theory, 106–17. Springer Berlin Heidelberg. doi:10.1007/3-540-44669-9_12.

See Also

• @stdlib/blas-ext/base/dsort2sh: simultaneously sort two double-precision floating-point strided arrays based on the sort order of the first array using Shellsort.
• @stdlib/blas-ext/base/gsortsh: sort a strided array using Shellsort.
• @stdlib/blas-ext/base/ssort2sh: simultaneously sort two single-precision floating-point strided arrays based on the sort order of the first array using Shellsort.

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.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.