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



NAME
       DGETRI

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



PURPOSE
            DGETRI computes the inverse of a matrix using the LU factorization
            computed by DGETRF.

            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 DOUBLE PRECISION array, dimension (LDA,N)
                     On entry, the factors L and U from the factorization
                     A = P*L*U as computed by DGETRF.
                     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 DGETRF; for 1<=i<=N, row i of the
                     matrix was interchanged with row IPIV(i).

           WORK      (output)
                     WORK is DOUBLE PRECISION 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                      DGETRI(3)