The routine may be called by the names f01vgf, nagf_matop_dtfttr or its LAPACK name dtfttr.
f01vgf unpacks a real triangular matrix , stored in RFP format to conventional storage in a full format array. This routine is intended for possible use in conjunction with routines from Chapters F06, F07 and F16 where some routines that use triangular matrices store them in RFP format.
The RFP storage format is described in Section 3.3.3 in the F07 Chapter Introduction.
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. Software37, 2
1: – Character(1)Input
On entry: specifies whether the normal RFP representation of or its transpose is stored.
The RFP representation of the matrix is stored.
The transpose of the RFP representation of the matrix is stored.
2: – Character(1)Input
On entry: specifies whether is upper or lower triangular.
is upper triangular.
is lower triangular.
3: – IntegerInput
On entry: , the order of the matrix .
4: – Real (Kind=nag_wp) arrayInput
On entry: the upper or lower triangular matrix (as specified by uplo) in either normal or transposed RFP format (as specified by transr). The storage format is described in Section 3.3.3 in the F07 Chapter Introduction.
5: – Real (Kind=nag_wp) arrayOutput
Note: the second dimension of the array a
must be at least
On exit: the triangular matrix .
If , is upper triangular and the elements of the array below the diagonal are not referenced.
If , is lower triangular and the elements of the array above the diagonal are not referenced.
6: – IntegerInput
On entry: the first dimension of the array a as declared in the (sub)program from which f01vgf is called.
7: – IntegerOutput
On exit: unless the routine detects an error (see Section 6).
6Error Indicators and Warnings
If , argument had an illegal value. An explanatory message is output, and execution of the program is terminated.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
f01vgf is not threaded in any implementation.
This example reads in a triangular matrix in RFP format and unpacks it to full format.