npm package: @stdlib/blas-ext-sorthp
Description: Sort an input ndarray along one or more ndarray dimensions using heapsort.
Author: The Stdlib Authors
Latest version: 0.1.1

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# sorthp

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> Sort an input [ndarray][@stdlib/ndarray/ctor] along one or more [ndarray][@stdlib/ndarray/ctor] dimensions using heapsort.

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-ext-sorthp
```

</section>

<section class="usage">

## Usage

```javascript
var sorthp = require( '@stdlib/blas-ext-sorthp' );
```

#### sorthp( x\[, sortOrder]\[, options] )

Sorts an input [ndarray][@stdlib/ndarray/ctor] along one or more [ndarray][@stdlib/ndarray/ctor] dimensions using heapsort.

```javascript
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );

var x = array( [ -1.0, 2.0, -3.0 ] );

var y = sorthp( x );
// returns <ndarray>

var arr = ndarray2array( y );
// returns [ -3.0, -1.0, 2.0 ]

var bool = ( x === y );
// returns true
```

The function has the following parameters:

-   **x**: input [ndarray][@stdlib/ndarray/ctor]. Must have a real-valued or "generic" [data type][@stdlib/ndarray/dtypes].
-   **sortOrder**: sort order (_optional_). May be either a scalar value, string, or an [ndarray][@stdlib/ndarray/ctor] having a real-valued or "generic" [data type][@stdlib/ndarray/dtypes]. If provided an [ndarray][@stdlib/ndarray/ctor], the value must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the complement of the shape defined by `options.dims`. For example, given the input shape `[2, 3, 4]` and `options.dims=[0]`, an [ndarray][@stdlib/ndarray/ctor] sort order must have a shape which is [broadcast-compatible][@stdlib/ndarray/base/broadcast-shapes] with the shape `[3, 4]`. Similarly, when performing the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor], an [ndarray][@stdlib/ndarray/ctor] sort order must be a zero-dimensional [ndarray][@stdlib/ndarray/ctor]. By default, the sort order is `1` (i.e., increasing order).
-   **options**: function options (_optional_).

The function accepts the following options:

-   **dims**: list of dimensions over which to perform operation. If not provided, the function performs the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor].

By default, the function sorts elements in increasing order. To sort in a different order, provide a `sortOrder` argument.

```javascript
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );

var x = array( [ -1.0, 2.0, -3.0 ] );

var y = sorthp( x, -1.0 );
// returns <ndarray>

var arr = ndarray2array( y );
// returns [ 2.0, -1.0, -3.0 ]
```

In addition to numeric values, one can specify the sort order via one of the following string literals: `'ascending'`, `'asc'`, `'descending'`, or `'desc'`. The first two literals indicate to sort in ascending (i.e., increasing) order. The last two literals indicate to sort in descending (i.e., decreasing) order.

```javascript
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );

var x = array( [ -1.0, 2.0, -3.0 ] );

// Sort in ascending order:
var y = sorthp( x, 'asc' );
// returns <ndarray>

var arr = ndarray2array( y );
// returns [ -3.0, -1.0, 2.0 ]

// Sort in descending order:
y = sorthp( x, 'descending' );
// returns <ndarray>

arr = ndarray2array( y );
// returns [ 2.0, -1.0, -3.0 ]
```

By default, the function performs the operation over all elements in a provided input [ndarray][@stdlib/ndarray/ctor]. To perform the operation over specific dimensions, provide a `dims` option.

```javascript
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var array = require( '@stdlib/ndarray-array' );

var x = array( [ -1.0, 2.0, -3.0, 4.0 ], {
    'shape': [ 2, 2 ],
    'order': 'row-major'
});

var v = ndarray2array( x );
// returns [ [ -1.0, 2.0 ], [ -3.0, 4.0 ] ]

var y = sorthp( x, {
    'dims': [ 0 ]
});
// returns <ndarray>

v = ndarray2array( y );
// returns [ [ -3.0, 2.0 ], [ -1.0, 4.0 ] ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   The input [ndarray][@stdlib/ndarray/ctor] is sorted **in-place** (i.e., the input [ndarray][@stdlib/ndarray/ctor] is **mutated**).
-   If `sortOrder < 0.0` or is either `'desc'` or `'descending'`, the input [ndarray][@stdlib/ndarray/ctor] is sorted in **decreasing** order. If `sortOrder > 0.0` or is either `'asc'` or `'ascending'`, the input [ndarray][@stdlib/ndarray/ctor] is sorted in **increasing** order. If `sortOrder == 0.0`, the input [ndarray][@stdlib/ndarray/ctor] is left 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 time complexity `O(N log2 N)`.
-   The algorithm is **unstable**, meaning that the algorithm may change the order of [ndarray][@stdlib/ndarray/ctor] elements which are equal or equivalent (e.g., `NaN` values).
-   The function iterates over [ndarray][@stdlib/ndarray/ctor] elements according to the memory layout of the input [ndarray][@stdlib/ndarray/ctor]. Accordingly, performance degradation is possible when operating over multiple dimensions of a large non-contiguous multi-dimensional input [ndarray][@stdlib/ndarray/ctor]. In such scenarios, one may want to copy an input [ndarray][@stdlib/ndarray/ctor] to contiguous memory before sorting.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var ndarray = require( '@stdlib/ndarray-ctor' );
var sorthp = require( '@stdlib/blas-ext-sorthp' );

// Generate an array of random numbers:
var xbuf = discreteUniform( 25, -20, 20, {
    'dtype': 'generic'
});

// Wrap in an ndarray:
var x = new ndarray( 'generic', xbuf, [ 5, 5 ], [ 5, 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

// Perform operation:
sorthp( x, {
    'dims': [ 0 ]
});

// Print the results:
console.log( ndarray2array( x ) );
```

</section>

<!-- /.examples -->

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<section class="related">

</section>

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## Notice

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

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## License

See [LICENSE][stdlib-license].


## Copyright

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