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NAME ZGETRI - compute the inverse of a matrix using the LU fac- torization computed by ZGETRF SYNOPSIS SUBROUTINE ZGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO ) INTEGER INFO, LDA, LWORK, N INTEGER IPIV( * ) COMPLEX*16 A( LDA, * ), WORK( LWORK ) PURPOSE ZGETRI computes the inverse of a matrix using the LU factor- ization computed by ZGETRF. This method inverts U and then computes inv(A) by solving the system inv(A)*L = inv(U) for inv(A). ARGUMENTS N (input) INTEGER The order of the matrix A. N >= 0. A (input/output) COMPLEX*16 array, dimension (LDA,N) On entry, the factors L and U from the factorization A = P*L*U as computed by ZGETRF. On exit, if INFO = 0, the inverse of the original matrix A. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,N). IPIV (input) INTEGER array, dimension (N) The pivot indices from ZGETRF; for 1<=i<=N, row i of the matrix was interchanged with row IPIV(i). WORK (workspace) COMPLEX*16 array, dimension (LWORK) On exit, if INFO=0, then WORK(1) returns the optimal LWORK. LWORK (input) INTEGER The dimension of the array WORK. LWORK >= max(1,N). For optimal performance LWORK >= N*NB, where NB is the optimal blocksize returned by ILAENV. INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, U(i,i) is exactly zero; the matrix is singular and its inverse could not be com- puted.