# cg.f

          SUBROUTINE CG (NM, N, AR, AI, WR, WI, MATZ, ZR, ZI, FV1, FV2, FV3,
         +   IERR)
    C***BEGIN PROLOGUE  CG
    C***PURPOSE  Compute the eigenvalues and, optionally, the eigenvectors
    C            of a complex general matrix.
    C***LIBRARY   SLATEC (EISPACK)
    C***CATEGORY  D4A4
    C***TYPE      COMPLEX (RG-S, CG-C)
    C***KEYWORDS  EIGENVALUES, EIGENVECTORS, EISPACK
    C***AUTHOR  Smith, B. T., et al.
    C***DESCRIPTION
    C
    C     This subroutine calls the recommended sequence of
    C     subroutines from the eigensystem subroutine package (EISPACK)
    C     to find the eigenvalues and eigenvectors (if desired)
    C     of a COMPLEX GENERAL matrix.
    C
    C     On INPUT
    C
    C        NM must be set to the row dimension of the two-dimensional
    C          array parameters, AR, AI, ZR and ZI, as declared in the
    C          calling program dimension statement.  NM is an INTEGER
    C          variable.
    C
    C        N is the order of the matrix A=(AR,AI).  N is an INTEGER
    C          variable.  N must be less than or equal to NM.
    C
    C        AR and AI contain the real and imaginary parts, respectively,
    C          of the complex general matrix.  AR and AI are two-dimensional
    C          REAL arrays, dimensioned AR(NM,N) and AI(NM,N).
    C
    C        MATZ is an INTEGER variable set equal to zero if only
    C          eigenvalues are desired.  Otherwise, it is set to any
    C          non-zero integer for both eigenvalues and eigenvectors.
    C
    C     On OUTPUT
    C
    C        WR and WI contain the real and imaginary parts, respectively,
    C          of the eigenvalues.  WR and WI are one-dimensional REAL
    C          arrays, dimensioned WR(N) and WI(N).
    C
    C        ZR and ZI contain the real and imaginary parts, respectively,
    C          of the eigenvectors if MATZ is not zero.  ZR and ZI are
    C          two-dimensional REAL arrays, dimensioned ZR(NM,N) and
    C          ZI(NM,N).
    C
    C        IERR is an INTEGER flag set to
    C          Zero       for normal return,
    C          10*N       if N is greater than NM,
    C          J          if the J-th eigenvalue has not been
    C                     determined after a total of 30 iterations.
    C                     The eigenvalues should be correct for indices
    C                     IERR+1, IERR+2, ..., N, but no eigenvectors are
    C                     computed.
    C
    C        FV1, FV2, and FV3 are one-dimensional REAL arrays used for
    C          temporary storage, dimensioned FV1(N), FV2(N), and FV3(N).
    C
    C     Questions and comments should be directed to B. S. Garbow,
    C     APPLIED MATHEMATICS DIVISION, ARGONNE NATIONAL LABORATORY
    C     ------------------------------------------------------------------
    C
    C***REFERENCES  B. T. Smith, J. M. Boyle, J. J. Dongarra, B. S. Garbow,
    C                 Y. Ikebe, V. C. Klema and C. B. Moler, Matrix Eigen-
    C                 system Routines - EISPACK Guide, Springer-Verlag,
    C                 1976.
    C***ROUTINES CALLED  CBABK2, CBAL, COMQR, COMQR2, CORTH
    C***REVISION HISTORY  (YYMMDD)
    C   760101  DATE WRITTEN
    C   890831  Modified array declarations.  (WRB)
    C   890831  REVISION DATE from Version 3.2
    C   891214  Prologue converted to Version 4.0 format.  (BAB)
    C   920501  Reformatted the REFERENCES section.  (WRB)
    C***END PROLOGUE  CG