README.md

dtrti2

Compute the inverse of a triangular matrix.

Usage

var dtrti2 = require( '@stdlib/lapack/base/dtrti2' );

dtrti2( order, uplo, diag, N, A, LDA )

Computes the inverse of a triangular matrix.

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

var A = new Float64Array( [ 1.0, 2.0, 0.0, 4.0 ] );
dtrti2( 'row-major', 'upper', 'non-unit', 2, A, 2 );
// A => <Float64Array>[ 1.0, -0.5, 0.0, 0.25 ]

The function has the following parameters:

• order: storage layout.
• uplo: specifies whether to copy the upper or lower triangular/trapezoidal part of a matrix A.
• diag: specifies whether or not A is unit triangular.
• N: order of matrix A.
• A: input 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 views.

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

// Initial arrays...
var A0 = new Float64Array( [ 0.0, 1.0, 2.0, 0.0, 4.0 ] );

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

dtrti2( 'row-major', 'upper', 'non-unit', 2, A1, 2 );
// A0 => <Float64Array>[ 0.0, 1.0, -0.5, 0.0, 0.25 ]

dtrti2.ndarray( uplo, diag, N, A, strideA1, strideA2, offsetA )

Computes the inverse of a triangular matrix using alternative indexing semantics.

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

var A = new Float64Array( [ 1.0, 2.0, 0.0, 4.0 ] );
dtrti2.ndarray( 'upper', 'non-unit', 2, A, 2, 1, 0 );
// A => <Float64Array>[ 1.0, -0.5, 0.0, 0.25 ]

The function has the following parameters:

• order: storage layout.
• uplo: specifies whether to copy the upper or lower triangular/trapezoidal part of a matrix A.
• diag: specifies whether or not A is unit triangular.
• N: order of matrix A.
• A: input Float64Array.
• sa1: stride of the first dimension of A.
• sa2: stride of the second dimension of A.
• oa: starting index for A.

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

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

var A = new Float64Array( [ 0.0, 0.0, 1.0, 2.0, 0.0, 4.0 ] );
dtrti2.ndarray( 'upper', 'non-unit', 2, A, 2, 1, 2 );
// A => <Float64Array>[ 0.0, 0.0, 1.0, -0.5, 0.0, 0.25 ]

Notes

• dtrti2() corresponds to the LAPACK routine dtrti2.

Examples

var Float64Array = require( '@stdlib/array/float64' );
var dtrti2 = require( '@stdlib/lapack/base/dtrti2' );

var A = new Float64Array( [ 1.0, 2.0, 0.0, 4.0 ] );
dtrti2( 'row-major', 'upper', 'non-unit', 2, A, 2 );
console.log( A );

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C APIs

Usage

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Examples

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