# cgeev.f

          SUBROUTINE CGEEV (A, LDA, N, E, V, LDV, WORK, JOB, INFO)
    C***BEGIN PROLOGUE  CGEEV
    C***PURPOSE  Compute the eigenvalues and, optionally, the eigenvectors
    C            of a complex general matrix.
    C***LIBRARY   SLATEC
    C***CATEGORY  D4A4
    C***TYPE      COMPLEX (SGEEV-S, CGEEV-C)
    C***KEYWORDS  EIGENVALUES, EIGENVECTORS, GENERAL MATRIX
    C***AUTHOR  Kahaner, D. K., (NBS)
    C           Moler, C. B., (U. of New Mexico)
    C           Stewart, G. W., (U. of Maryland)
    C***DESCRIPTION
    C
    C     Abstract
    C      CGEEV computes the eigenvalues and, optionally,
    C      the eigenvectors of a general complex matrix.
    C
    C     Call Sequence Parameters-
    C       (The values of parameters marked with * (star) will be changed
    C         by CGEEV.)
    C
    C        A*      COMPLEX(LDA,N)
    C                complex nonsymmetric input matrix.
    C
    C        LDA     INTEGER
    C                set by the user to
    C                the leading dimension of the complex array A.
    C
    C        N       INTEGER
    C                set by the user to
    C                the order of the matrices A and V, and
    C                the number of elements in E.
    C
    C        E*      COMPLEX(N)
    C                on return from CGEEV E contains the eigenvalues of A.
    C                See also INFO below.
    C
    C        V*      COMPLEX(LDV,N)
    C                on return from CGEEV if the user has set JOB
    C                = 0        V is not referenced.
    C                = nonzero  the N eigenvectors of A are stored in the
    C                first N columns of V.  See also INFO below.
    C                (If the input matrix A is nearly degenerate, V
    C                 will be badly conditioned, i.e. have nearly
    C                 dependent columns.)
    C
    C        LDV     INTEGER
    C                set by the user to
    C                the leading dimension of the array V if JOB is also
    C                set nonzero.  In that case N must be .LE. LDV.
    C                If JOB is set to zero LDV is not referenced.
    C
    C        WORK*   REAL(3N)
    C                temporary storage vector.  Contents changed by CGEEV.
    C
    C        JOB     INTEGER
    C                set by the user to
    C                = 0        eigenvalues only to be calculated by CGEEV.
    C                           neither V nor LDV are referenced.
    C                = nonzero  eigenvalues and vectors to be calculated.
    C                           In this case A & V must be distinct arrays.
    C                           Also,  if LDA > LDV,  CGEEV changes all the
    C                           elements of A thru column N.  If LDA < LDV,
    C                           CGEEV changes all the elements of V through
    C                           column N.  If LDA = LDV only A(I,J) and V(I,
    C                           J) for I,J = 1,...,N are changed by CGEEV.
    C
    C        INFO*   INTEGER
    C                on return from CGEEV the value of INFO is
    C                = 0  normal return, calculation successful.
    C                = K  if the eigenvalue iteration fails to converge,
    C                     eigenvalues K+1 through N are correct, but
    C                     no eigenvectors were computed even if they were
    C                     requested (JOB nonzero).
    C
    C      Error Messages
    C           No. 1  recoverable  N is greater than LDA
    C           No. 2  recoverable  N is less than one.
    C           No. 3  recoverable  JOB is nonzero and N is greater than LDV
    C           No. 4  warning      LDA > LDV,  elements of A other than the
    C                               N by N input elements have been changed
    C           No. 5  warning      LDA < LDV,  elements of V other than the
    C                               N by N output elements have been changed
    C
    C***REFERENCES  (NONE)
    C***ROUTINES CALLED  CBABK2, CBAL, COMQR, COMQR2, CORTH, SCOPY, XERMSG
    C***REVISION HISTORY  (YYMMDD)
    C   800808  DATE WRITTEN
    C   890531  Changed all specific intrinsics to generic.  (WRB)
    C   890531  REVISION DATE from Version 3.2
    C   891214  Prologue converted to Version 4.0 format.  (BAB)
    C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
    C   900326  Removed duplicate information from DESCRIPTION section.
    C           (WRB)
    C***END PROLOGUE  CGEEV