ZGETRI(3)      LAPACK routine of NEC Numeric Library Collection      ZGETRI(3)



NAME
       ZGETRI

SYNOPSIS
       SUBROUTINE ZGETRI (N, A, LDA, IPIV, WORK, LWORK, INFO)



PURPOSE
            ZGETRI computes the inverse of a matrix using the LU factorization
            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)
                     N is INTEGER
                     The order of the matrix A.  N >= 0.

           A         (input/output)
                     A is 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)
                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           IPIV      (input)
                     IPIV is 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      (output)
                     WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
                     On exit, if INFO=0, then WORK(1) returns the optimal LWORK.

           LWORK     (input)
                     LWORK is 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.

                     If LWORK = -1, then a workspace query is assumed; the routine
                     only calculates the optimal size of the WORK array, returns
                     this value as the first entry of the WORK array, and no error
                     message related to LWORK is issued by XERBLA.

           INFO      (output)
                     INFO is 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 computed.



LAPACK routine                  31 October 2017                      ZGETRI(3)