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NAME ZTRTRI - compute the inverse of a complex upper or lower triangular matrix A SYNOPSIS SUBROUTINE ZTRTRI( UPLO, DIAG, N, A, LDA, INFO ) CHARACTER DIAG, UPLO INTEGER INFO, LDA, N COMPLEX*16 A( LDA, * ) PURPOSE ZTRTRI computes the inverse of a complex upper or lower tri- angular matrix A. This is the Level 3 BLAS version of the algorithm. ARGUMENTS UPLO (input) CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular. DIAG (input) CHARACTER*1 = 'N': A is non-unit triangular; = 'U': A is unit triangular. N (input) INTEGER The order of the matrix A. N >= 0. A (input/output) COMPLEX*16 array, dimension (LDA,N) On entry, the triangular matrix A. If UPLO = 'U', the leading N-by-N upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading N-by-N lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1. On exit, the (triangular) inverse of the original matrix, in the same storage format. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,N). INFO (output) 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 tri- angular matrix is singular and its inverse can not be computed.