ztptri()

subroutine ztptri	(	character	uplo,
		character	diag,
		integer	n,
		complex*16, dimension( * )	ap,
		integer	info )

ZTPTRI

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Purpose:

!>
!> ZTPTRI computes the inverse of a complex upper or lower triangular
!> matrix A stored in packed format.
!> 

Parameters

[in]	UPLO	!> UPLO is CHARACTER*1 !> = 'U': A is upper triangular; !> = 'L': A is lower triangular. !>
[in]	DIAG	!> DIAG is CHARACTER*1 !> = 'N': A is non-unit triangular; !> = 'U': A is unit triangular. !>
[in]	N	!> N is INTEGER !> The order of the matrix A. N >= 0. !>
[in,out]	AP	!> AP is COMPLEX*16 array, dimension (N*(N+1)/2) !> 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. !>
[out]	INFO	!> 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.

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
!>