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168 changes: 168 additions & 0 deletions lib/node_modules/@stdlib/blas/ext/base/gsort/README.md
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<!--

@license Apache-2.0

Copyright (c) 2026 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

-->

# gsort

> Sort a strided array.

<section class="usage">

## Usage

```javascript
var gsort = require( '@stdlib/blas/ext/base/gsort' );
```

#### gsort( N, order, x, strideX )

Sorts a strided array.

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort( 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. If `order < 0.0`, the input strided array is sorted in **decreasing** order. If `order > 0.0`, the input strided array is sorted in **increasing** order. If `order == 0.0`, the input strided array is left unchanged.
- **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
- **strideX**: stride length.

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

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort( 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, use [`typed array`][mdn-typed-array] views.

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

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

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

// Sort every other element...
gsort( 2, -1.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 4.0, 3.0, 2.0 ]
```

#### gsort.ndarray( N, order, x, strideX, offsetX )

Sorts a strided array using alternative indexing semantics.

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0 ];

gsort.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.

While [`typed array`][mdn-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:

```javascript
var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];

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

</section>

<!-- /.usage -->

<section class="notes">

## Notes

- If `N <= 0` or `order == 0.0`, both functions return `x` 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 input strided array is sorted **in-place** (i.e., the input strided array is **mutated**).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

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

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

gsort( x.length, -1.0, x, -1 );
console.log( x );
```

</section>

<!-- /.examples -->

<section class="references">

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

<!-- <related-links> -->

<!-- </related-links> -->

</section>

<!-- /.links -->
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/**
* @license Apache-2.0
*
* Copyright (c) 2026 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var bench = require( '@stdlib/bench' );
var uniform = require( '@stdlib/random/array/uniform' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var pow = require( '@stdlib/math/base/special/pow' );
var floor = require( '@stdlib/math/base/special/floor' );
var format = require( '@stdlib/string/format' );
var pkg = require( './../package.json' ).name;
var gsort = require( './../lib/main.js' );


// FUNCTIONS //

/**
* Create a benchmark function.
*
* @private
* @param {PositiveInteger} iter - number of iterations
* @param {PositiveInteger} len - array length
* @returns {Function} benchmark function
*/
function createBenchmark( iter, len ) {
var tmp;
var x;
var i;

x = [];
for ( i = 0; i < iter; i++ ) {
tmp = uniform( len, -100.0, 100.0, {
'dtype': 'generic'
});
x.push( tmp );
}
return benchmark;

/**
* Benchmark function.
*
* @private
* @param {Benchmark} b - benchmark instance
*/
function benchmark( b ) {
var xc;
var y;
var i;

xc = x.slice();
for ( i = 0; i < iter; i++ ) {
xc[ i ] = x[ i ].slice();
}
b.tic();
for ( i = 0; i < b.iterations; i++ ) {
y = gsort( len, 1, xc[ i ], 1 );
if ( isnan( y[ i%len ] ) ) {
b.fail( 'should not return NaN' );
}
}
b.toc();
if ( isnan( y[ i%len ] ) ) {
b.fail( 'should not return NaN' );
}
b.pass( 'benchmark finished' );
b.end();
}
}


// MAIN //

function main() {
var opts;
var iter;
var len;
var min;
var max;
var f;
var i;

iter = 1e6;
min = 1; // 10^min
max = 4; // 10^max

for ( i = min; i <= max; i++ ) {
len = pow( 10, i );
f = createBenchmark( iter, len );
opts = {
'iterations': iter
};
bench( format( '%s::unsorted,random:len=%d', pkg, len ), opts, f );
iter = floor( pow( iter, 3.0/4.0 ) );
}
}

main();
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