## MB04AD

### Eigenvalues of a real skew-Hamiltonian/Hamiltonian pencil in factored form

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

      To compute the eigenvalues of a real N-by-N skew-Hamiltonian/
      Hamiltonian pencil aS - bH with

                                       (  0  I  )
        S = T Z = J Z' J' Z, where J = (        ),                   (1)
                                       ( -I  0  )

      via generalized symplectic URV decomposition. That is, orthogonal
      matrices Q1 and Q2 and orthogonal symplectic matrices U1 and U2
      are computed such that

                                    ( T11  T12 )
        Q1' T U1 = Q1' J Z' J' U1 = (          ) = Tout,
                                    (  0   T22 )

                   ( Z11  Z12 )
        U2' Z Q2 = (          ) = Zout,                              (2)
                   (  0   Z22 )

                   ( H11  H12 )
        Q1' H Q2 = (          ) = Hout,
                   (  0   H22 )

      where T11, T22', Z11, Z22', H11 are upper triangular and H22' is
      upper quasi-triangular. The notation M' denotes the transpose of
      the matrix M.
      Optionally, if COMPQ1 = 'I' or COMPQ1 = 'U', the orthogonal
      transformation matrix Q1 will be computed.
      Optionally, if COMPQ2 = 'I' or COMPQ2 = 'U', the orthogonal
      transformation matrix Q2 will be computed.
      Optionally, if COMPU1 = 'I' or COMPU1 = 'U', the orthogonal
      symplectic transformation matrix

             (  U11  U12  )
        U1 = (            )
             ( -U12  U11  )

      will be computed.
      Optionally, if COMPU2 = 'I' or COMPU2 = 'U', the orthogonal
      symplectic transformation matrix

             (  U21  U22  )
        U2 = (            )
             ( -U22  U21  )

      will be computed.

Specification

          SUBROUTINE MB04AD( JOB, COMPQ1, COMPQ2, COMPU1, COMPU2, N, Z, LDZ,
         $                   H, LDH, Q1, LDQ1, Q2, LDQ2, U11, LDU11, U12,
         $                   LDU12, U21, LDU21, U22, LDU22, T, LDT, ALPHAR,
         $                   ALPHAI, BETA, IWORK, LIWORK, DWORK, LDWORK,
         $                   INFO )
    C     .. Scalar Arguments ..
          CHARACTER          COMPQ1, COMPQ2, COMPU1, COMPU2, JOB
          INTEGER            INFO, LDH, LDQ1, LDQ2, LDT, LDU11, LDU12,
         $                   LDU21, LDU22, LDWORK, LDZ, LIWORK, N
    C     .. Array Arguments ..
          INTEGER            IWORK( * )
          DOUBLE PRECISION   ALPHAI( * ), ALPHAR( * ), BETA( * ),
         $                   DWORK( * ), H( LDH, * ), Q1( LDQ1, * ),
         $                   Q2( LDQ2, * ), T( LDT, * ), U11( LDU11, * ),
         $                   U12( LDU12, * ), U21( LDU21, * ),
         $                   U22( LDU22, * ), Z( LDZ, * )

Arguments

Mode Parameters

      JOB     CHARACTER*1
              Specifies the computation to be performed, as follows:
              = 'E': compute the eigenvalues only; Z, T, and H will not
                     necessarily be put into the forms in (2); H22' is
                     upper Hessenberg;
              = 'T': put Z, T, and H into the forms in (2), and return
                     the eigenvalues in ALPHAR, ALPHAI and BETA.

      COMPQ1  CHARACTER*1
              Specifies whether to compute the orthogonal transformation
              matrix Q1, as follows:
              = 'N': Q1 is not computed;
              = 'I': the array Q1 is initialized internally to the unit
                     matrix, and the orthogonal matrix Q1 is returned;
              = 'U': the array Q1 contains an orthogonal matrix Q01 on
                     entry, and the product Q01*Q1 is returned, where Q1
                     is the product of the orthogonal transformations
                     that are applied to the pencil aT*Z - bH on the
                     left to reduce T, Z, and H to the forms in (2),
                     for COMPQ1 = 'I'.

      COMPQ2  CHARACTER*1
              Specifies whether to compute the orthogonal transformation
              matrix Q2, as follows:
              = 'N': Q2 is not computed;
              = 'I': the array Q2 is initialized internally to the unit
                     matrix, and the orthogonal matrix Q2 is returned;
              = 'U': the array Q2 contains an orthogonal matrix Q02 on
                     entry, and the product Q02*Q2 is returned, where Q2
                     is the product of the orthogonal transformations
                     that are applied to the pencil aT*Z - bH on the
                     right to reduce T, Z, and H to the forms in (2),
                     for COMPQ2 = 'I'.

      COMPU1  CHARACTER*1
              Specifies whether to compute the orthogonal symplectic
              transformation matrix U1, as follows:
              = 'N': U1 is not computed;
              = 'I': the arrays U11 and U12 are initialized internally
                     to the unit and zero matrices, respectively, and
                     the corresponding submatrices of the orthogonal
                     symplectic matrix U1 are returned;
              = 'U': the arrays U11 and U12 contain the corresponding
                     submatrices of an orthogonal symplectic matrix U01
                     on entry, and the updated submatrices U11 and U12
                     of the matrix product U01*U1 are returned, where U1
                     is the product of the orthogonal symplectic
                     transformations that are applied to the pencil
                     aT*Z - bH to reduce T, Z, and H to the forms in
                     (2), for COMPU1 = 'I'.

      COMPU2  CHARACTER*1
              Specifies whether to compute the orthogonal symplectic
              transformation matrix U2, as follows:
              = 'N': U2 is not computed;
              = 'I': the arrays U21 and U22 are initialized internally
                     to the unit and zero matrices, respectively, and
                     the corresponding submatrices of the orthogonal
                     symplectic matrix U2 are returned;
              = 'U': the arrays U21 and U22 contain the corresponding
                     submatrices of an orthogonal symplectic matrix U02
                     on entry, and the updated submatrices U21 and U22
                     of the matrix product U02*U2 are returned, where U2
                     is the product of the orthogonal symplectic
                     transformations that are applied to the pencil
                     aT*Z - bH to reduce T, Z, and H to the forms in
                     (2), for COMPU2 = 'I'.

Input/Output Parameters

      N       (input) INTEGER
              The order of the pencil aS - bH.  N >= 0, even.

      Z       (input/output) DOUBLE PRECISION array, dimension (LDZ, N)
              On entry, the leading N-by-N part of this array must
              contain the matrix Z.
              On exit, if JOB = 'T', the leading N-by-N part of this
              array contains the matrix Zout; otherwise, it contains the
              matrix Z obtained just before the application of the
              periodic QZ algorithm.
              The elements of the (2,1) block, i.e., in the rows N/2+1
              to N and in the columns 1 to N/2 are not set to zero, but
              are unchanged on exit.

      LDZ     INTEGER
              The leading dimension of the array Z.  LDZ >= MAX(1, N).

      H       (input/output) DOUBLE PRECISION array, dimension (LDH, N)
              On entry, the leading N-by-N part of this array must
              contain the Hamiltonian matrix H (H22 = -H11', H12 = H12',
              H21 = H21').
              On exit, if JOB = 'T', the leading N-by-N part of this
              array contains the matrix Hout; otherwise, it contains the
              matrix H obtained just before the application of the
              periodic QZ algorithm.

      LDH     INTEGER
              The leading dimension of the array H.  LDH >= MAX(1, N).

      Q1      (input/output) DOUBLE PRECISION array, dimension (LDQ1, N)
              On entry, if COMPQ1 = 'U', then the leading N-by-N part of
              this array must contain a given matrix Q01, and on exit,
              the leading N-by-N part of this array contains the product
              of the input matrix Q01 and the transformation matrix Q1
              used to transform the matrices Z, T and H.
              On exit, if COMPQ1 = 'I', then the leading N-by-N part of
              this array contains the orthogonal transformation matrix
              Q1.
              If COMPQ1 = 'N', this array is not referenced.

      LDQ1    INTEGER
              The leading dimension of the array Q1.
              LDQ1 >= 1,         if COMPQ1 = 'N';
              LDQ1 >= MAX(1, N), if COMPQ1 = 'I' or COMPQ1 = 'U'.

      Q2      (input/output) DOUBLE PRECISION array, dimension (LDQ2, N)
              On entry, if COMPQ2 = 'U', then the leading N-by-N part of
              this array must contain a given matrix Q02, and on exit,
              the leading N-by-N part of this array contains the product
              of the input matrix Q02 and the transformation matrix Q2
              used to transform the matrices Z, T and H.
              On exit, if COMPQ2 = 'I', then the leading N-by-N part of
              this array contains the orthogonal transformation matrix
              Q2.
              If COMPQ2 = 'N', this array is not referenced.

      LDQ2    INTEGER
              The leading dimension of the array Q2.
              LDQ2 >= 1,         if COMPQ2 = 'N';
              LDQ2 >= MAX(1, N), if COMPQ2 = 'I' or COMPQ2 = 'U'.

      U11     (input/output) DOUBLE PRECISION array, dimension
                             (LDU11, N/2)
              On entry, if COMPU1 = 'U', then the leading N/2-by-N/2
              part of this array must contain the upper left block of a
              given matrix U01, and on exit, the leading N/2-by-N/2 part
              of this array contains the updated upper left block U11 of
              the product of the input matrix U01 and the transformation
              matrix U1 used to transform the matrices Z, T, and H.
              On exit, if COMPU1 = 'I', then the leading N/2-by-N/2 part
              of this array contains the upper left block U11 of the
              orthogonal symplectic transformation matrix U1.
              If COMPU1 = 'N' this array is not referenced.

      LDU11   INTEGER
              The leading dimension of the array U11.
              LDU11 >= 1,           if COMPU1 = 'N';
              LDU11 >= MAX(1, N/2), if COMPU1 = 'I' or COMPU1 = 'U'.

      U12     (input/output) DOUBLE PRECISION array, dimension
                             (LDU12, N/2)
              On entry, if COMPU1 = 'U', then the leading N/2-by-N/2
              part of this array must contain the upper right block of a
              given matrix U01, and on exit, the leading N/2-by-N/2 part
              of this array contains the updated upper right block U12
              of the product of the input matrix U01 and the
              transformation matrix U1 used to transform the matrices
              Z, T, and H.
              On exit, if COMPU1 = 'I', then the leading N/2-by-N/2 part
              of this array contains the upper right block U12 of the
              orthogonal symplectic transformation matrix U1.
              If COMPU1 = 'N' this array is not referenced.

      LDU12   INTEGER
              The leading dimension of the array U12.
              LDU12 >= 1,           if COMPU1 = 'N';
              LDU12 >= MAX(1, N/2), if COMPU1 = 'I' or COMPU1 = 'U'.

      U21     (input/output) DOUBLE PRECISION array, dimension
                             (LDU21, N/2)
              On entry, if COMPU2 = 'U', then the leading N/2-by-N/2
              part of this array must contain the upper left block of a
              given matrix U02, and on exit, the leading N/2-by-N/2 part
              of this array contains the updated upper left block U21 of
              the product of the input matrix U02 and the transformation
              matrix U2 used to transform the matrices Z, T, and H.
              On exit, if COMPU2 = 'I', then the leading N/2-by-N/2 part
              of this array contains the upper left block U21 of the
              orthogonal symplectic transformation matrix U2.
              If COMPU2 = 'N' this array is not referenced.

      LDU21   INTEGER
              The leading dimension of the array U21.
              LDU21 >= 1,           if COMPU2 = 'N';
              LDU21 >= MAX(1, N/2), if COMPU2 = 'I' or COMPU2 = 'U'.

      U22     (input/output) DOUBLE PRECISION array, dimension
                             (LDU22, N/2)
              On entry, if COMPU2 = 'U', then the leading N/2-by-N/2
              part of this array must contain the upper right block of a
              given matrix U02, and on exit, the leading N/2-by-N/2 part
              of this array contains the updated upper right block U22
              of the product of the input matrix U02 and the
              transformation matrix U2 used to transform the matrices
              Z, T, and H.
              On exit, if COMPU2 = 'I', then the leading N/2-by-N/2 part
              of this array contains the upper right block U22 of the
              orthogonal symplectic transformation matrix U2.
              If COMPU2 = 'N' this array is not referenced.

      LDU22   INTEGER
              The leading dimension of the array U22.
              LDU22 >= 1,           if COMPU2 = 'N';
              LDU22 >= MAX(1, N/2), if COMPU2 = 'I' or COMPU2 = 'U'.

      T       (output) DOUBLE PRECISION array, dimension (LDT, N)
              If JOB = 'T', the leading N-by-N part of this array
              contains the matrix Tout; otherwise, it contains the
              matrix T obtained just before the application of the
              periodic QZ algorithm.

      LDT     INTEGER
              The leading dimension of the array T.  LDT >= MAX(1, N).

      ALPHAR  (output) DOUBLE PRECISION array, dimension (N/2)
              The real parts of each scalar alpha defining an eigenvalue
              of the pencil aS - bH.

      ALPHAI  (output) DOUBLE PRECISION array, dimension (N/2)
              The imaginary parts of each scalar alpha defining an
              eigenvalue of the pencil aS - bH.
              If ALPHAI(j) is zero, then the j-th eigenvalue is real.

      BETA    (output) DOUBLE PRECISION array, dimension (N/2)
              The scalars beta defining the eigenvalues of the pencil
              aS - bH.
              Together, the quantities alpha = (ALPHAR(j),ALPHAI(j)) and
              beta = BETA(j) represent the j-th eigenvalue of the pencil
              aS - bH, in the form lambda = alpha/beta. Since lambda may
              overflow, the ratios should not, in general, be computed.
              Due to the skew-Hamiltonian/Hamiltonian structure of the
              pencil, for every eigenvalue lambda, -lambda is also an
              eigenvalue, and thus it has only to be saved once in
              ALPHAR, ALPHAI and BETA.
              Specifically, only eigenvalues with imaginary parts
              greater than or equal to zero are stored; their conjugate
              eigenvalues are not stored. If imaginary parts are zero
              (i.e., for real eigenvalues), only positive eigenvalues
              are stored. The remaining eigenvalues have opposite signs.
              As a consequence, pairs of complex eigenvalues, stored in
              consecutive locations, are not complex conjugate.

Workspace

      IWORK   INTEGER array, dimension (LIWORK)
              On exit, if INFO = 3, IWORK(1) contains the number of
              (pairs of) possibly inaccurate eigenvalues, q <= N/2, and
              IWORK(2), ..., IWORK(q+1) indicate their indices.
              Specifically, a positive value is an index of a real or
              purely imaginary eigenvalue, corresponding to a 1-by-1
              block, while the absolute value of a negative entry in
              IWORK is an index to the first eigenvalue in a pair of
              consecutively stored eigenvalues, corresponding to a
              2-by-2 block. A 2-by-2 block may have two complex, two
              real, two purely imaginary, or one real and one purely
              imaginary eigenvalue.
              For i = q+2, ..., 2*q+1, IWORK(i) contains a pointer to
              the starting location in DWORK of the i-th quadruple of
              1-by-1 blocks, if IWORK(i-q) > 0, or 2-by-2 blocks,
              if IWORK(i-q) < 0, defining unreliable eigenvalues.
              IWORK(2*q+2) contains the number of the 1-by-1 blocks, and
              IWORK(2*q+3) contains the number of the 2-by-2 blocks,
              corresponding to unreliable eigenvalues. IWORK(2*q+4)
              contains the total number t of the 2-by-2 blocks.
              If INFO = 0, then q = 0, therefore IWORK(1) = 0.

      LIWORK  INTEGER
              The dimension of the array IWORK.   LIWORK >= N+18.

      DWORK   DOUBLE PRECISION array, dimension (LDWORK)
              On exit, if INFO = 0 or INFO = 3, DWORK(1) returns the
              optimal LDWORK, and DWORK(2), ..., DWORK(7) contain the
              Frobenius norms of the factors of the formal matrix
              product used by the algorithm. In addition, DWORK(8), ...,
              DWORK(7+6*s) contain the s sextuple values corresponding
              to the 1-by-1 blocks. Their eigenvalues are real or purely
              imaginary. Such an eigenvalue is obtained from
              -i*sqrt((a1/a2/a3)*(a4/a5/a6)), but always taking a
              positive sign, where a1, ..., a6 are the corresponding
              sextuple values.
              Moreover, DWORK(8+6*s), ..., DWORK(7+6*s+24*t) contain the
              t groups of sextuple 2-by-2 matrices corresponding to the
              2-by-2 blocks. Their eigenvalue pairs are either complex,
              or placed on the real and imaginary axes. Such an
              eigenvalue pair is obtained as -1i*sqrt(ev), but taking
              positive imaginary parts, where ev are the eigenvalues of
              the product A1*inv(A2)*inv(A3)*A4*inv(A5)*inv(A6), where
              A1, ..., A6 define the corresponding 2-by-2 matrix
              sextuple.
              On exit, if INFO = -31, DWORK(1) returns the minimum value
              of LDWORK.

      LDWORK  INTEGER
              The dimension of the array DWORK.
              If JOB = 'E' and COMPQ1 = 'N' and COMPQ2 = 'N' and
              COMPU1 = 'N' and COMPU2 = 'N', then
                    LDWORK >= 3/2*N**2 + MAX(6*N,54);
              else, LDWORK >=   3*N**2 + MAX(6*N,54).
              For good performance LDWORK should generally be larger.

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

Error Indicator

      INFO    INTEGER
              = 0: succesful exit;
              < 0: if INFO = -i, the i-th argument had an illegal value;
              = 1: the periodic QZ algorithm was not able to reveal
                   information about the eigenvalues from the 2-by-2
                   blocks in the SLICOT Library routine MB03BD;
              = 2: the periodic QZ algorithm did not converge in the
                   SLICOT Library routine MB03BD;
              = 3: some eigenvalues might be inaccurate, and details can
                   be found in IWORK and DWORK. This is a warning.

Method

      The algorithm uses Givens rotations and Householder reflections to
      annihilate elements in T, Z, and H such that T11, T22', Z11, Z22',
      and H11 are upper triangular and H22' is upper Hessenberg. Finally
      the periodic QZ algorithm is applied to transform H22' to upper
      quasi-triangular form while T11, T22', Z11, Z22', and H11 stay in
      upper triangular form.
      See also page 17 in [1] for more details.

References

      [1] Benner, P., Byers, R., Losse, P., Mehrmann, V. and Xu, H.
          Numerical Solution of Real Skew-Hamiltonian/Hamiltonian
          Eigenproblems.
          Tech. Rep., Technical University Chemnitz, Germany,
          Nov. 2007.

Numerical Aspects

                                                                3
      The algorithm is numerically backward stable and needs O(N ) real
      floating point operations.

Further Comments

      None

Example

Program Text

    *     MB04AD EXAMPLE PROGRAM TEXT
    *
    *     .. Parameters ..
          INTEGER            NIN, NOUT
          PARAMETER          ( NIN = 5, NOUT = 6 )
          INTEGER            NMAX
          PARAMETER          ( NMAX = 50 )
          INTEGER            LDH, LDQ1, LDQ2, LDT, LDU11, LDU12, LDU21,
         $                   LDU22, LDWORK, LDZ, LIWORK
          PARAMETER          ( LDH = NMAX, LDQ1  = NMAX,   LDQ2 = NMAX,
         $                     LDT = NMAX, LDU11 = NMAX/2, LDU12 = NMAX/2,
         $                     LDU21  = NMAX/2, LDU22 = NMAX/2,
         $                     LDWORK = 3*NMAX*NMAX + MAX( NMAX, 48 ) + 6,
         $                     LDZ = NMAX,  LIWORK = NMAX + 18 )
          DOUBLE PRECISION  ZERO
          PARAMETER         ( ZERO = 0.0D0 )
    *
    *     .. Local Scalars ..
          CHARACTER          COMPQ1, COMPQ2, COMPU1, COMPU2, JOB
          INTEGER            I, INFO, J, M, N
    *
    *     .. Local Arrays ..
          INTEGER            IWORK( LIWORK )
          DOUBLE PRECISION   ALPHAI( NMAX/2 ), ALPHAR( NMAX/2 ),
         $                   BETA( NMAX/2 ), DWORK( LDWORK ),
         $                   H( LDH, NMAX ), Q1( LDQ1, NMAX ),
         $                   Q2( LDQ2, NMAX ), T( LDT, NMAX ),
         $                   U11( LDU11, NMAX/2 ), U12( LDU12, NMAX/2 ),
         $                   U21( LDU21, NMAX/2 ), U22( LDU22, NMAX/2 ),
         $                   Z( LDZ, NMAX )
    *
    *     .. External Functions ..
          LOGICAL            LSAME
          EXTERNAL           LSAME
    *
    *     .. External Subroutines ..
          EXTERNAL           DLASET, MB04AD
    *
    *     .. Intrinsic Functions ..
          INTRINSIC          MAX
    *
    *     .. Executable Statements ..
    *
          WRITE( NOUT, FMT = 99999 )
    *     Skip the heading in the data file and read in the data.
          READ( NIN, FMT = * )
          READ( NIN, FMT = * ) JOB, COMPQ1, COMPQ2, COMPU1, COMPU2, N
          IF( N.LT.0 .OR. N.GT.NMAX ) THEN
             WRITE( NOUT, FMT = 99998 ) N
          ELSE
             READ( NIN, FMT = * ) ( ( Z( I, J ), J = 1, N ), I = 1, N )
             READ( NIN, FMT = * ) ( ( H( I, J ), J = 1, N ), I = 1, N )
    *        Compute the eigenvalues of a real skew-Hamiltonian/Hamiltonian
    *        pencil (factored version).
             CALL MB04AD( JOB, COMPQ1, COMPQ2, COMPU1, COMPU2, N, Z, LDZ, H,
         $                LDH, Q1, LDQ1, Q2, LDQ2, U11, LDU11, U12, LDU12,
         $                U21, LDU21, U22, LDU22, T, LDT, ALPHAR, ALPHAI,
         $                BETA, IWORK, LIWORK, DWORK, LDWORK, INFO )
    *
             IF( INFO.NE.0 ) THEN
                WRITE( NOUT, FMT = 99997 ) INFO
             ELSE
                M = N/2
                CALL DLASET( 'Full', M, M, ZERO, ZERO, Z( M+1, 1 ), LDZ )
                WRITE( NOUT, FMT = 99996 )
                DO 10 I = 1, N
                   WRITE( NOUT, FMT = 99995 ) ( T( I, J ), J = 1, N )
       10       CONTINUE
                WRITE( NOUT, FMT = 99994 )
                DO 20 I = 1, N
                   WRITE( NOUT, FMT = 99995 ) ( Z( I, J ), J = 1, N )
       20       CONTINUE
                WRITE( NOUT, FMT = 99993 )
                DO 30 I = 1, N
                   WRITE( NOUT, FMT = 99995 ) ( H( I, J ), J = 1, N )
       30       CONTINUE
                IF( LSAME( COMPQ1, 'I' ) ) THEN
                   WRITE( NOUT, FMT = 99992 )
                   DO 40 I = 1, N
                      WRITE( NOUT, FMT = 99995 ) ( Q1( I, J ), J = 1, N )
       40          CONTINUE
                END IF
                IF( LSAME( COMPQ2, 'I' ) ) THEN
                   WRITE( NOUT, FMT = 99991 )
                   DO 50 I = 1, N
                      WRITE( NOUT, FMT = 99995 ) ( Q2( I, J ), J = 1, N )
       50          CONTINUE
                END IF
                IF( LSAME( COMPU1, 'I' ) ) THEN
                   WRITE( NOUT, FMT = 99990 )
                   DO 60 I = 1, M
                      WRITE( NOUT, FMT = 99995 ) ( U11( I, J ), J = 1, M )
       60          CONTINUE
                   WRITE( NOUT, FMT = 99989 )
                   DO 70 I = 1, M
                      WRITE( NOUT, FMT = 99995 ) ( U12( I, J ), J = 1, M )
       70          CONTINUE
                END IF
                IF( LSAME( COMPU2, 'I' ) ) THEN
                   WRITE( NOUT, FMT = 99988 )
                   DO 80 I = 1, M
                      WRITE( NOUT, FMT = 99995 ) ( U21( I, J ), J = 1, M )
       80          CONTINUE
                   WRITE( NOUT, FMT = 99987 )
                   DO 90 I = 1, M
                      WRITE( NOUT, FMT = 99995 ) ( U22( I, J ), J = 1, M )
       90          CONTINUE
                END IF
                WRITE( NOUT, FMT = 99986 )
                WRITE( NOUT, FMT = 99995 ) ( ALPHAR( I ), I = 1, M )
                WRITE( NOUT, FMT = 99985 )
                WRITE( NOUT, FMT = 99995 ) ( ALPHAI( I ), I = 1, M )
                WRITE( NOUT, FMT = 99984 )
                WRITE( NOUT, FMT = 99995 ) (   BETA( I ), I = 1, M )
             END IF
          END IF
          STOP
    *
    99999 FORMAT( 'MB04AD EXAMPLE PROGRAM RESULTS', 1X )
    99998 FORMAT( 'N is out of range.', /, 'N = ', I5 )
    99997 FORMAT( 'INFO on exit from MB04AD = ', I2 )
    99996 FORMAT( 'The matrix T on exit is ' )
    99995 FORMAT( 50( 1X, F8.4 ) )
    99994 FORMAT( 'The matrix Z on exit is ' )
    99993 FORMAT( 'The matrix H is ' )
    99992 FORMAT( 'The matrix Q1 is ' )
    99991 FORMAT( 'The matrix Q2 is ' )
    99990 FORMAT( 'The upper left block of the matrix U1 is ' )
    99989 FORMAT( 'The upper right block of the matrix U1 is ' )
    99988 FORMAT( 'The upper left block of the matrix U2 is ' )
    99987 FORMAT( 'The upper right block of the matrix U2 is ' )
    99986 FORMAT( 'The vector ALPHAR is ' )
    99985 FORMAT( 'The vector ALPHAI is ' )
    99984 FORMAT( 'The vector BETA is ' )
          END

Program Data

    MB04AD EXAMPLE PROGRAM DATA
       T   I   I   I   I   8
       3.1472    4.5751   -0.7824    1.7874   -2.2308   -0.6126    2.0936    4.5974
       4.0579    4.6489    4.1574    2.5774   -4.5383   -1.1844    2.5469   -1.5961
      -3.7301   -3.4239    2.9221    2.4313   -4.0287    2.6552   -2.2397    0.8527
       4.1338    4.7059    4.5949   -1.0777    3.2346    2.9520    1.7970   -2.7619
       1.3236    4.5717    1.5574    1.5548    1.9483   -3.1313    1.5510    2.5127
      -4.0246   -0.1462   -4.6429   -3.2881   -1.8290   -0.1024   -3.3739   -2.4490
      -2.2150    3.0028    3.4913    2.0605    4.5022   -0.5441   -3.8100    0.0596
       0.4688   -3.5811    4.3399   -4.6817   -4.6555    1.4631   -0.0164    1.9908
       3.9090   -3.5071    3.1428   -3.0340   -1.4834    3.7401   -0.1715    0.4026
       4.5929   -2.4249   -2.5648   -2.4892    3.7401   -2.1416    1.6251    2.6645
       0.4722    3.4072    4.2926    1.1604   -0.1715    1.6251   -4.2415   -0.0602
      -3.6138   -2.4572   -1.5002   -0.2671    0.4026    2.6645   -0.0602   -3.7009
       0.6882   -1.8421   -4.1122    0.1317   -3.9090   -4.5929   -0.4722    3.6138
      -1.8421    2.9428   -0.4340    1.3834    3.5071    2.4249   -3.4072    2.4572
      -4.1122   -0.4340   -2.3703    0.5231   -3.1428    2.5648   -4.2926    1.5002
       0.1317    1.3834    0.5231   -4.1618    3.0340    2.4892   -1.1604    0.2671

Program Results

    MB04AD EXAMPLE PROGRAM RESULTS
    The matrix T on exit is
      -3.9699   3.7658   5.5815  -1.7750  -0.8818  -0.0511  -4.2158   1.9054
       0.0000   5.3686  -5.9166   4.9163   1.3839   0.8870   3.9458  -4.9167
       0.0000   0.0000   5.9641   1.9432  -2.0680   2.4402  -1.4091   5.8512
       0.0000   0.0000   0.0000   5.9983  -3.8172   4.0147  -2.0739  -1.2570
       0.0000   0.0000   0.0000   0.0000   8.2005   0.0000   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000   1.5732   8.0098   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000   0.6017   2.4397   5.9751   0.0000
       0.0000   0.0000   0.0000   0.0000  -2.5869   0.5598   0.2544   5.2129
    The matrix Z on exit is
      -6.4705  -2.5511  -4.0551  -1.9895  -2.7642   0.7532  -4.1047  -2.2046
       0.0000   7.3589  -4.4480  -2.7491  -1.5465  -1.4345  -0.9272   1.3121
       0.0000   0.0000   4.9125  -0.4968   5.3574   3.8579   5.2547  -1.7324
       0.0000   0.0000   0.0000   9.0822   0.0460  -0.3382   3.9302   3.1084
       0.0000   0.0000   0.0000   0.0000   6.1869   0.0000   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000   5.5573   6.6549   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000   2.7456  -3.5789   4.3432   0.0000
       0.0000   0.0000   0.0000   0.0000   0.1549   3.5335   3.1346   4.1062
    The matrix H is
      -7.4834   0.4404   2.3558   1.6724  -0.4630   1.9533   1.5724  -2.7254
       0.0000  -7.3500   3.7414   3.7466   0.2837   0.6849   0.7727  -4.2140
       0.0000   0.0000  -2.3493  -3.7994  -0.6872   1.1773  -2.6901  -5.1494
       0.0000   0.0000   0.0000  -3.4719   5.3322   0.4182   1.9779   1.5175
       0.0000   0.0000   0.0000   0.0000  -6.1880   0.0000   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000  -3.3324   9.0833   0.0000   0.0000
       0.0000   0.0000   0.0000   0.0000  -1.8703   0.0799  -2.8180   0.0000
       0.0000   0.0000   0.0000   0.0000  -2.3477   3.3110   0.6561   0.7281
    The matrix Q1 is
      -0.2489  -0.1409   0.3615   0.6458   0.0113   0.6063  -0.0470   0.0238
      -0.2436   0.1294  -0.0874  -0.4103   0.3408   0.3628  -0.3267   0.6272
      -0.4316  -0.2352   0.5553  -0.2811  -0.2198  -0.2880  -0.4564  -0.1773
       0.1992  -0.2176  -0.5198   0.1561  -0.1523   0.1299  -0.7281  -0.2197
       0.0161   0.7390   0.1125  -0.2226  -0.1003   0.3608  -0.1118  -0.4886
      -0.5824   0.0984  -0.3052   0.1996   0.5889  -0.2442   0.0060  -0.3341
      -0.3246   0.4661  -0.1835   0.3523  -0.5153  -0.3034  -0.0865   0.3931
      -0.4559  -0.2961  -0.3790  -0.3127  -0.4356   0.3452   0.3642  -0.1467
    The matrix Q2 is
       0.0288  -0.1842  -0.6791  -0.2115  -0.4790   0.4212  -0.0417  -0.2253
      -0.0666  -0.0787  -0.3711   0.1737  -0.0482  -0.5770  -0.6785   0.1607
       0.1506   0.6328   0.0518  -0.6266   0.0652  -0.0790  -0.2854  -0.2994
      -0.2900  -0.2737  -0.0076  -0.3671  -0.2017  -0.6241   0.4521  -0.2675
       0.3353   0.4107   0.0326   0.1400  -0.6447  -0.2043   0.2561   0.4187
       0.0905  -0.1648  -0.2363  -0.5323   0.3180   0.0286   0.1252   0.7126
      -0.7246   0.0468   0.3328  -0.1794  -0.3639   0.2257  -0.2623   0.2786
       0.4922  -0.5353   0.4803  -0.2501  -0.2723   0.0199  -0.3194  -0.0371
    The upper left block of the matrix U1 is
       0.4144   0.2249   0.6015  -0.1964
      -0.0198   0.5131  -0.2823  -0.3058
      -0.6620   0.1508   0.2237   0.0240
      -0.0743  -0.4323  -0.0332  -0.7263
    The upper right block of the matrix U1 is
      -0.3474   0.1306  -0.3391  -0.3530
      -0.3760   0.1550   0.6087  -0.1646
       0.1707   0.6553  -0.1262  -0.1177
       0.3048  -0.0773   0.0767  -0.4173
    The upper left block of the matrix U2 is
       0.1403  -0.6447  -0.6536  -0.3707
       0.7069   0.2609  -0.0091  -0.1702
      -0.1218  -0.1120   0.3766  -0.5154
       0.0773   0.6349  -0.5070  -0.1810
    The upper right block of the matrix U2 is
       0.0000   0.0000   0.0000   0.0000
       0.1182   0.1587   0.1930  -0.5716
       0.6051  -0.2720   0.3364   0.1089
       0.2823  -0.0386  -0.1529   0.4434
    The vector ALPHAR is
       0.0000   0.7122   0.0000   0.7450
    The vector ALPHAI is
       0.7540   0.0000   0.7465   0.0000
    The vector BETA is
       4.0000   4.0000   8.0000  16.0000

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