npm package: @stdlib/lapack-base-iladlr
Description: LAPACK routine to find the index of the last non-zero row in an input matrix.
Author: The Stdlib Authors
Latest version: 0.1.1

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# iladlr

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Find the index of the last non-zero row in a matrix `A`.

<section class="installation">

## Installation

```bash
npm install @stdlib/lapack-base-iladlr
```

</section>

<section class="usage">

## Usage

```javascript
var iladlr = require( '@stdlib/lapack-base-iladlr' );
```

#### iladlr( order, M, N, A, LDA )

Returns the index of the last non-zero row in a matrix `A`.

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

var A = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 0.0, 0.0 ] );

/*
    A = [
        [ 1.0, 2.0 ],
        [ 3.0, 4.0 ],
        [ 0.0, 0.0 ]
    ]
*/

var out = iladlr( 'row-major', 3, 2, A, 2 );
// returns 1
```

The function has the following parameters:

-   **order**: storage layout.
-   **M**: number of rows in `A`.
-   **N**: number of columns in `A`.
-   **A**: input [`Float64Array`][mdn-float64array].
-   **LDA**: stride of the first dimension of `A` (a.k.a., leading dimension of the matrix `A`).

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

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

// Initial array:
var A0 = new Float64Array( [ 9999.0, 1.0, 2.0, 3.0, 4.0, 0.0, 0.0 ] );

// Create an offset view:
var A1 = new Float64Array( A0.buffer, A0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var out = iladlr( 'row-major', 3, 2, A1, 2 );
// returns 1
```

#### iladlr.ndarray( M, N, A, strideA1, strideA2, offsetA )

Returns the index of the last non-zero row in a matrix `A` using alternative indexing semantics.

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

var A = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 0.0, 0.0 ] );

/*
    A = [
        [ 1.0, 2.0 ],
        [ 3.0, 4.0 ],
        [ 0.0, 0.0 ]
    ]
*/

var out = iladlr.ndarray( 3, 2, A, 2, 1, 0 );
// returns 1
```

The function has the following parameters:

-   **M**: number of rows in `A`.
-   **N**: number of columns in `A`.
-   **A**: input [`Float64Array`][mdn-float64array].
-   **strideA1**: stride of the first dimension of `A`.
-   **strideA2**: stride of the second dimension of `A`.
-   **offsetA**: starting index for `A`.

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,

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

var A = new Float64Array( [ 9999.0, 1.0, 2.0, 3.0, 4.0, 0.0, 0.0 ] );

/*
    A = [
        [ 1.0, 2.0 ],
        [ 3.0, 4.0 ],
        [ 0.0, 0.0 ]
    ]
*/

var out = iladlr.ndarray( 3, 2, A, 2, 1, 1 );
// returns 1
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   This routine is commonly used throughout LAPACK to shrink work domains (e.g., before bulge-chasing, deflation, or when trimming Householder panels), thus ensuring that higher-level routines operate only on numerically relevant sub-matrices.
-   `iladlr()` corresponds to the [LAPACK][lapack] routine [`iladlr`][lapack-iladlr].

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var ndarray2array = require( '@stdlib/ndarray-base-to-array' );
var Float64Array = require( '@stdlib/array-float64' );
var shape2strides = require( '@stdlib/ndarray-base-shape2strides' );
var iladlr = require( '@stdlib/lapack-base-iladlr' );

var shape = [ 3, 3 ];
var order = 'row-major';
var strides = shape2strides( shape, order );

var A = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 0.0, 0.0, 0.0 ] );
console.log( ndarray2array( A, shape, strides, 0, order ) );

var out = iladlr( order, shape[ 0 ], shape[ 1 ], A, strides[ 0 ] );
console.log( out );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
TODO
```

#### TODO

TODO.

```c
TODO
```

TODO

```c
TODO
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
TODO
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

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[umd]: https://github.com/umdjs/umd
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[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/lapack-base-iladlr/main/LICENSE

[lapack]: https://www.netlib.org/lapack/explore-html/

[lapack-iladlr]: https://www.netlib.org/lapack/explore-html/da/d60/group__ilalr_gadb53a9bd5cc7a6e3bbca7bf4eca32208.html

[mdn-float64array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Float64Array

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

</section>

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