LAPACK routine to find the index of the last non-zero column in an input matrix.
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> Find the index of the last non-zero column in a matrix A.
``bash`
npm install @stdlib/lapack-base-iladlc
`javascript`
var iladlc = require( '@stdlib/lapack-base-iladlc' );
#### iladlc( order, M, N, A, LDA )
Returns the index of the last non-zero column in a matrix A.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var A = new Float64Array( [ 1.0, 2.0, 0.0, 3.0, 4.0, 0.0 ] );
/*
A = [
[ 1.0, 2.0, 0.0 ],
[ 3.0, 4.0, 0.0 ]
]
*/
var out = iladlc( 'row-major', 2, 3, A, 3 );
// returns 1
`
The function has the following parameters:
- order: storage layout.
- M: number of rows in A.A
- N: number of columns in .Float64Array
- A: input [][mdn-float64array].A
- LDA: stride of the first dimension of (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.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
// Initial array:
var A0 = new Float64Array( [ 9999.0, 1.0, 2.0, 0.0, 3.0, 4.0, 0.0 ] );
// Create an offset view:
var A1 = new Float64Array( A0.buffer, A0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var out = iladlc( 'row-major', 2, 3, A1, 3 );
// returns 1
`
#### iladlc.ndarray( M, N, A, strideA1, strideA2, offsetA )
Returns the index of the last non-zero column in a matrix A using alternative indexing semantics.
`javascript
var Float64Array = require( '@stdlib/array-float64' );
var A = new Float64Array( [ 1.0, 2.0, 0.0, 3.0, 4.0, 0.0 ] );
/*
A = [
[ 1.0, 2.0, 0.0 ],
[ 3.0, 4.0, 0.0 ]
]
*/
var out = iladlc.ndarray( 2, 3, A, 3, 1, 0 );
// returns 1
`
The function has the following parameters:
- M: number of rows in A.A
- N: number of columns in .Float64Array
- A: input [][mdn-float64array].A
- strideA1: stride of the first dimension of .A
- strideA2: stride of the second dimension of .A
- offsetA: starting index for .
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, 0.0, 3.0, 4.0, 0.0 ] );
/*
A = [
[ 1.0, 2.0, 0.0 ],
[ 3.0, 4.0, 0.0 ]
]
*/
var out = iladlc.ndarray( 2, 3, A, 3, 1, 1 );
// returns 1
`
- 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.
- iladlc() corresponds to the [LAPACK][lapack] routine [iladlc][lapack-iladlc].
`javascript
var ndarray2array = require( '@stdlib/ndarray-base-to-array' );
var Float64Array = require( '@stdlib/array-float64' );
var shape2strides = require( '@stdlib/ndarray-base-shape2strides' );
var iladlc = require( '@stdlib/lapack-base-iladlc' );
var shape = [ 3, 3 ];
var order = 'row-major';
var strides = shape2strides( shape, order );
var A = new Float64Array( [ 1.0, 2.0, 0.0, 3.0, 4.0, 0.0, 5.0, 6.0, 0.0 ] );
console.log( ndarray2array( A, shape, strides, 0, order ) );
var out = iladlc( order, shape[ 0 ], shape[ 1 ], A, strides[ 0 ] );
console.log( out );
`
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`c`
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*
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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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---
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/lapack-base-iladlc/tree/deno
[deno-readme]: https://github.com/stdlib-js/lapack-base-iladlc/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/lapack-base-iladlc/tree/umd
[umd-readme]: https://github.com/stdlib-js/lapack-base-iladlc/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/lapack-base-iladlc/tree/esm
[esm-readme]: https://github.com/stdlib-js/lapack-base-iladlc/blob/esm/README.md
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[lapack]: https://www.netlib.org/lapack/explore-html/
[lapack-iladlc]: https://www.netlib.org/lapack/explore-html/dc/df6/group__ilalc_gad8c407910f229795fe7a074b98be9338.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