Usage

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

#### dpttrf( N, D, E )

Computes the L D L^T factorization of a real symmetric positive definite tridiagonal matrix A.

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

var D = new Float64Array( [ 4.0, 5.0, 6.0 ] );
var E = new Float64Array( [ 1.0, 2.0 ] );

dpttrf( 3, D, E );
// D => [ 4, 4.75, ~5.15789 ]
// E => [ 0.25, ~0.4210 ]
`

The function has the following parameters:

- N: order of matrix A.
- D: the N diagonal elements of A as a [Float64Array][mdn-float64array].
- E: the N-1 subdiagonal elements of A as a [Float64Array][mdn-float64array].

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 arrays...
var D0 = new Float64Array( [ 0.0, 4.0, 5.0, 6.0 ] );
var E0 = new Float64Array( [ 0.0, 1.0, 2.0 ] );

// Create offset views...
var D1 = new Float64Array( D0.buffer, D0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var E1 = new Float64Array( E0.buffer, E0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

dpttrf( 3, D1, E1 );
// D0 => [ 0.0, 4.0, 4.75, ~5.15789 ]
// E0 => [ 0.0, 0.25, ~0.4210 ]
`

#### dpttrf.ndarray( N, D, strideD, offsetD, E, strideE, offsetE )

Computes the L D L^T factorization of a real symmetric positive definite tridiagonal matrix A using alternative indexing semantics.

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

var D = new Float64Array( [ 4.0, 5.0, 6.0 ] );
var E = new Float64Array( [ 1.0, 2.0 ] );

dpttrf.ndarray( 3, D, 1, 0, E, 1, 0 );
// D => [ 4, 4.75, ~5.15789 ]
// E => [ 0.25, ~0.4210 ]
`

The function has the following additional parameters:

- strideD: stride length for D.
- offsetD: starting index for D.
- strideE: stride length for E.
- offsetE: starting index for E.

While [typed array][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example,

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

var D = new Float64Array( [ 0.0, 4.0, 5.0, 6.0 ] );
var E = new Float64Array( [ 0.0, 1.0, 2.0 ] );

dpttrf.ndarray( 3, D, 1, 1, E, 1, 1 );
// D => [ 0.0, 4.0, 4.75, ~5.15789 ]
// E => [ 0.0, 0.25, ~0.4210 ]
`