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.TH ZTPTRI l "15 June 2000" "LAPACK version 3.0" ")"
.SH NAME
ZTPTRI - compute the inverse of a complex upper or lower triangular matrix A stored in packed format
.SH SYNOPSIS
.TP 19
SUBROUTINE ZTPTRI(
UPLO, DIAG, N, AP, INFO )
.TP 19
.ti +4
CHARACTER
DIAG, UPLO
.TP 19
.ti +4
INTEGER
INFO, N
.TP 19
.ti +4
COMPLEX*16
AP( * )
.SH PURPOSE
ZTPTRI computes the inverse of a complex upper or lower triangular matrix A stored in packed format.
.SH ARGUMENTS
.TP 8
UPLO (input) CHARACTER*1
= 'U': A is upper triangular;
.br
= 'L': A is lower triangular.
.TP 8
DIAG (input) CHARACTER*1
.br
= 'N': A is non-unit triangular;
.br
= 'U': A is unit triangular.
.TP 8
N (input) INTEGER
The order of the matrix A. N >= 0.
.TP 8
AP (input/output) 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.
.TP 8
INFO (output) INTEGER
= 0: successful exit
.br
< 0: if INFO = -i, the i-th argument had an illegal value
.br
> 0: if INFO = i, A(i,i) is exactly zero. The triangular
matrix is singular and its inverse can not be computed.
.SH FURTHER DETAILS
A triangular matrix A can be transferred to packed storage using one
of the following program segments:
.br
UPLO = 'U': UPLO = 'L':
.br
JC = 1 JC = 1
.br
DO 2 J = 1, N DO 2 J = 1, N
.br
DO 1 I = 1, J DO 1 I = J, N
.br
AP(JC+I-1) = A(I,J) AP(JC+I-J) = A(I,J)
1 CONTINUE 1 CONTINUE
.br
JC = JC + J JC = JC + N - J + 1
2 CONTINUE 2 CONTINUE
.br
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