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

Alternatively,

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To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

vargsortsh=require('@stdlib/blas-ext-base-gsortsh');

Sorts a strided array using Shellsort.

varx=[1.0,-2.0,3.0,-4.0];gsortsh(x.length,1.0,x,1);// x => [ -4.0, -2.0, 1.0, 3.0 ]

The function has the following parameters:

• N: number of indexed elements.
• order: sort order. Iforder < 0.0, the input strided array is sorted indecreasing order. Iforder > 0.0, the input strided array is sorted inincreasing order. Iforder == 0.0, the input strided array is left unchanged.
• x: inputArray ortyped array.
• strideX: stride length.

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

varx=[1.0,-2.0,3.0,-4.0];gsortsh(2,-1.0,x,2);// x => [ 3.0, -2.0, 1.0, -4.0 ]

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

varFloat64Array=require('@stdlib/array-float64');// Initial array...varx0=newFloat64Array([1.0,2.0,3.0,4.0]);// Create an offset view...varx1=newFloat64Array(x0.buffer,x0.BYTES_PER_ELEMENT*1);// start at 2nd element// Sort every other element...gsortsh(2,-1.0,x1,2);// x0 => <Float64Array>[ 1.0, 4.0, 3.0, 2.0 ]

Sorts a strided array using Shellsort and alternative indexing semantics.

varx=[1.0,-2.0,3.0,-4.0];gsortsh.ndarray(x.length,1.0,x,1,0);// x => [ -4.0, -2.0, 1.0, 3.0 ]

The function has the following additional parameters:

• offsetX: starting index.

Whiletyped 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:

varx=[1.0,-2.0,3.0,-4.0,5.0,-6.0];gsortsh.ndarray(3,1.0,x,1,x.length-3);// x => [ 1.0, -2.0, 3.0, -6.0, -4.0, 5.0 ]

• IfN <= 0 ororder == 0.0, both functions returnx 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 sortsNaN 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 complexityO(1) and worst case time complexityO(N^(4/3)).
• The algorithm is efficient forshorter strided arrays (typicallyN <= 50).
• The algorithm isunstable, meaning that the algorithm may change the order of strided array elements which are equal or equivalent (e.g.,NaN values).
• The input strided array is sortedin-place (i.e., the input strided array ismutated).
• Depending on the environment, the typed versions (dsortsh,ssortsh, etc.) are likely to be significantly more performant.

• 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." InFundamentals of Computation Theory, 106–17. Springer Berlin Heidelberg. doi:10.1007/3-540-44669-9_12.

• @stdlib/blas-ext/base/dsortsh:sort a double-precision floating-point strided array using Shellsort.
• @stdlib/blas-ext/base/gsort2sh:simultaneously sort two strided arrays based on the sort order of the first array using Shellsort.
• @stdlib/blas-ext/base/ssortsh:sort a single-precision floating-point strided array using Shellsort.

This package is part ofstdlib, 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 developstdlib, see the main projectrepository.

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