naginterfaces.library.matop.dtrttf

naginterfaces.library.matop.dtrttf(transr, uplo, a)

dtrttf copies a real triangular matrix, stored in a full format array, to a Rectangular Full Packed (RFP) format array.

For full information please refer to the NAG Library document for f01ve

https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f01/f01vef.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.

afloat, array-like, shape $(n,n)$

The triangular matrix $A$.

Returns

arfloat, ndarray, 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.

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 $\text{n}$.

Constraint: $n\ge 0$.

Notes

dtrttf packs a real $n\times n$ triangular matrix $A$, stored conventionally in a full format array, into RFP 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.

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)