SLATEC Routines --- CHIEV ---

*DECK CHIEV
      SUBROUTINE CHIEV (A, LDA, N, E, V, LDV, WORK, JOB, INFO)
C***BEGIN PROLOGUE  CHIEV
C***PURPOSE  Compute the eigenvalues and, optionally, the eigenvectors
C            of a complex Hermitian matrix.
C***LIBRARY   SLATEC
C***CATEGORY  D4A3
C***TYPE      COMPLEX (SSIEV-S, CHIEV-C)
C***KEYWORDS  COMPLEX HERMITIAN, EIGENVALUES, EIGENVECTORS, MATRIX,
C             SYMMETRIC
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     David Kahaner, Cleve Moler, G. W. Stewart,
C       N.B.S.         U.N.M.      N.B.S./U.MD.
C
C     Abstract
C      CHIEV computes the eigenvalues and, optionally,
C      the eigenvectors of a complex Hermitian matrix.
C
C     Call Sequence Parameters-
C       (the values of parameters marked with * (star) will be changed
C         by CHIEV.)
C
C        A*      COMPLEX(LDA,N)
C                complex Hermitian input matrix.
C                Only the upper triangle of A need be
C                filled in.  Elements on diagonal must be real.
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*      REAL(N)
C                on return from CHIEV E contains the eigenvalues of A.
C                See also INFO below.
C
C        V*      COMPLEX(LDV,N)
C                on return from CHIEV 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
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(4N)
C                temporary storage vector.  Contents changed by CHIEV.
C
C        JOB     INTEGER
C                set by the user to
C                = 0        eigenvalues only to be calculated by CHIEV.
C                           Neither V nor LDV are referenced.
C                = nonzero  eigenvalues and vectors to be calculated.
C                           In this case A and V must be distinct arrays
C                           also if LDA .GT. LDV CHIEV changes all the
C                           elements of A thru column N.  If LDA < LDV
C                           CHIEV 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 CHIEV.
C
C        INFO*   INTEGER
C                on return from CHIEV the value of INFO is
C                = 0  normal return, calculation successful.
C                = K  if the eigenvalue iteration fails to converge,
C                     eigenvalues (and eigenvectors if requested)
C                     1 through K-1 are correct.
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           No. 6  recoverable  nonreal element on diagonal of A.
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  HTRIBK, HTRIDI, IMTQL2, SCOPY, SCOPYM, TQLRAT,
C                    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***END PROLOGUE  CHIEV