CTPTRI (3) Linux Manual Page
ctptri.f –
Synopsis
Functions/Subroutines
subroutine ctptri (UPLO, DIAG, N, AP, INFO)CTPTRI
Function/Subroutine Documentation
subroutine ctptri (characterUPLO, characterDIAG, integerN, complex, dimension( * )AP, integerINFO)
CTPTRI Purpose:
CTPTRI computes the inverse of a complex upper or lower triangular
matrix A stored in packed format.
Parameters:
- UPLO
UPLO is CHARACTER*1
DIAG
= ‘U’: A is upper triangular;
= ‘L’: A is lower triangular.DIAG is CHARACTER*1
N
= ‘N’: A is non-unit triangular;
= ‘U’: A is unit triangular.N is INTEGER
AP
The order of the matrix A. N >= 0.AP is COMPLEX array, dimension (N*(N+1)/2)
INFO
On entry, the upper or lower triangular matrix A, stored
columnwise in a linear array. The j-th column of A is stored
in the array AP as follows:
if UPLO = ‘U’, AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
if UPLO = ‘L’, AP(i + (j-1)*((2*n-j)/2) = A(i,j) for j<=i<=n.
See below for further details.
On exit, the (triangular) inverse of the original matrix, in
the same packed storage format.INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, A(i,i) is exactly zero. The triangular
matrix is singular and its inverse can not be computed.
Author:
- Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
- November 2011
Further Details:
A triangular matrix A can be transferred to packed storage using one
of the following program segments:
UPLO = ‘U’: UPLO = ‘L’:
JC = 1 JC = 1
DO 2 J = 1, N DO 2 J = 1, N
DO 1 I = 1, J DO 1 I = J, N
AP(JC+I-1) = A(I,J) AP(JC+I-J) = A(I,J)
1 CONTINUE 1 CONTINUE
JC = JC + J JC = JC + N – J + 1
2 CONTINUE 2 CONTINUE
Definition at line 118 of file ctptri.f.