naginterfaces.library.matop.dtfttp

naginterfaces.library.matop.dtfttp(transr, uplo, n, ar)

dtfttp copies a real triangular matrix, stored in a Rectangular Full Packed (RFP) format array, to a standard packed format array.

For full information please refer to the NAG Library document for f01vl

https://support.nag.com/numeric/nl/nagdoc_30.3/flhtml/f01/f01vlf.html

Parameters

transrstr, length 1

Specifies whether the normal RFP representation of $A$ or its transpose is stored.

$transr=\text{'N'}$

The RFP representation of the matrix $A$ is stored.

$transr=\text{'T'}$

The transpose of the RFP representation of the matrix $A$ is stored.

uplostr, length 1

Specifies whether $A$ is upper or lower triangular.

$uplo=\text{'U'}$

$A$ is upper triangular.

$uplo=\text{'L'}$

$A$ is lower triangular.

nint

$n$, the order of the matrix $A$.

arfloat, array-like, shape $(n\times (n+1)/2)$

The upper or lower $n\times n$ triangular matrix $A$ (as specified by $uplo$) in either normal or transposed RFP format (as specified by $transr$). The storage format is described in the F07 Introduction.

Returns

apfloat, ndarray, shape $(n\times (n+1)/2)$

The $n\times n$ triangular matrix $A$, packed by columns.

Raises

NagValueError

(errno $-1$)

On entry, error in parameter $transr$.

Constraint: $transr=\text{'N'}$ or $\text{'T'}$.

(errno $-2$)

On entry, error in parameter $uplo$.

Constraint: $uplo=\text{'U'}$ or $\text{'L'}$.

(errno $-3$)

On entry, error in parameter $n$.

Constraint: $n\ge 0$.

Notes

dtfttp packs a real $n\times n$ triangular matrix $A$, stored in RFP format, to packed format. This function is intended for possible use in conjunction with functions from submodule blas, submodule blast and submodule lapacklin where some functions that use triangular matrices store them in RFP format. The RFP storage format is described in the F07 Introduction and the packed storage format is described in the F07 Introduction.

References

Gustavson, F G, Waśniewski, J, Dongarra, J J and Langou, J, 2010, Rectangular full packed format for Cholesky’s algorithm: factorization, solution, and inversion, ACM Trans. Math. Software (37, 2)