#include "f2c.h"
#include "netlib.h"
extern double sqrt(double); /* #include <math.h> */

/* Table of constant values */
static integer c__1 = 1;
static integer c__2 = 2;
static doublereal c_b28 = 1.;

/* Subroutine */ void dtgsen_(ijob, wantq, wantz, select, n, a, lda, b, ldb,
        alphar, alphai, beta, q, ldq, z, ldz, m, pl, pr, dif, work, lwork, iwork, liwork, info)
integer *ijob;
logical *wantq, *wantz, *select;
integer *n;
doublereal *a;
integer *lda;
doublereal *b;
integer *ldb;
doublereal *alphar, *alphai, *beta, *q;
integer *ldq;
doublereal *z;
integer *ldz, *m;
doublereal *pl, *pr, *dif, *work;
integer *lwork, *iwork, *liwork, *info;
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, q_dim1, q_offset, z_dim1, z_offset, i__1;
    doublereal d__1;

    /* Local variables */
    static integer kase;
    static logical pair;
    static integer ierr;
    static doublereal dsum;
    static logical swap;
    static integer i, k;
    static logical wantd;
    static integer lwmin;
    static logical wantp;
    static integer n1, n2;
    static logical wantd1, wantd2;
    static integer kk;
    static doublereal dscale;
    static integer ks;
    static doublereal rdscal;
    static integer liwmin;
    static doublereal smlnum;
    static integer mn2;
    static logical lquery;
    static integer ijb;
    static doublereal eps;

/*  -- LAPACK routine (version 3.0) --                                    */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,        */
/*     Courant Institute, Argonne National Lab, and Rice University       */
/*     June 30, 1999                                                      */
/*                                                                        */
/*  Purpose                                                               */
/*  =======                                                               */
/*                                                                        */
/*  DTGSEN reorders the generalized real Schur decomposition of a real    */
/*  matrix pair (A, B) (in terms of an orthonormal equivalence trans-     */
/*  formation Q' * (A, B) * Z), so that a selected cluster of eigenvalues */
/*  appears in the leading diagonal blocks of the upper quasi-triangular  */
/*  matrix A and the upper triangular B. The leading columns of Q and     */
/*  Z form orthonormal bases of the corresponding left and right eigen-   */
/*  spaces (deflating subspaces). (A, B) must be in generalized real      */
/*  Schur canonical form (as returned by DGGES), i.e. A is block upper    */
/*  triangular with 1-by-1 and 2-by-2 diagonal blocks. B is upper         */
/*  triangular.                                                           */
/*                                                                        */
/*  DTGSEN also computes the generalized eigenvalues                      */
/*                                                                        */
/*              w(j) = (ALPHAR(j) + i*ALPHAI(j))/BETA(j)                  */
/*                                                                        */
/*  of the reordered matrix pair (A, B).                                  */
/*                                                                        */
/*  Optionally, DTGSEN computes the estimates of reciprocal condition     */
/*  numbers for eigenvalues and eigenspaces. These are Difu[(A11,B11),    */
/*  (A22,B22)] and Difl[(A11,B11), (A22,B22)], i.e. the separation(s)     */
/*  between the matrix pairs (A11, B11) and (A22,B22) that correspond to  */
/*  the selected cluster and the eigenvalues outside the cluster, resp.,  */
/*  and norms of "projections" onto left and right eigenspaces w.r.t.     */
/*  the selected cluster in the (1,1)-block.                              */
/*                                                                        */
/*  Arguments                                                             */
/*  =========                                                             */
/*                                                                        */
/*  IJOB    (input) INTEGER                                               */
/*          Specifies whether condition numbers are required for the      */
/*          cluster of eigenvalues (PL and PR) or the deflating subspaces */
/*          (Difu and Difl):                                              */
/*           =0: Only reorder w.r.t. SELECT. No extras.                   */
/*           =1: Reciprocal of norms of "projections" onto left and right */
/*               eigenspaces w.r.t. the selected cluster (PL and PR).     */
/*           =2: Upper bounds on Difu and Difl. F-norm-based estimate     */
/*               (DIF(1:2)).                                              */
/*           =3: Estimate of Difu and Difl. 1-norm-based estimate         */
/*               (DIF(1:2)).                                              */
/*               About 5 times as expensive as IJOB = 2.                  */
/*           =4: Compute PL, PR and DIF (i.e. 0, 1 and 2 above): Economic */
/*               version to get it all.                                   */
/*           =5: Compute PL, PR and DIF (i.e. 0, 1 and 3 above)           */
/*                                                                        */
/*  WANTQ   (input) LOGICAL                                               */
/*          .TRUE. : update the left transformation matrix Q;             */
/*          .FALSE.: do not update Q.                                     */
/*                                                                        */
/*  WANTZ   (input) LOGICAL                                               */
/*          .TRUE. : update the right transformation matrix Z;            */
/*          .FALSE.: do not update Z.                                     */
/*                                                                        */
/*  SELECT  (input) LOGICAL array, dimension (N)                          */
/*          SELECT specifies the eigenvalues in the selected cluster.     */
/*          To select a real eigenvalue w(j), SELECT(j) must be set to    */
/*          .TRUE.. To select a complex conjugate pair of eigenvalues     */
/*          w(j) and w(j+1), corresponding to a 2-by-2 diagonal block,    */
/*          either SELECT(j) or SELECT(j+1) or both must be set to        */
/*          .TRUE.; a complex conjugate pair of eigenvalues must be       */
/*          either both included in the cluster or both excluded.         */
/*                                                                        */
/*  N       (input) INTEGER                                               */
/*          The order of the matrices A and B. N >= 0.                    */
/*                                                                        */
/*  A       (input/output) DOUBLE PRECISION array, dimension(LDA,N)       */
/*          On entry, the upper quasi-triangular matrix A, with (A, B) in */
/*          generalized real Schur canonical form.                        */
/*          On exit, A is overwritten by the reordered matrix A.          */
/*                                                                        */
/*  LDA     (input) INTEGER                                               */
/*          The leading dimension of the array A. LDA >= max(1,N).        */
/*                                                                        */
/*  B       (input/output) DOUBLE PRECISION array, dimension(LDB,N)       */
/*          On entry, the upper triangular matrix B, with (A, B) in       */
/*          generalized real Schur canonical form.                        */
/*          On exit, B is overwritten by the reordered matrix B.          */
/*                                                                        */
/*  LDB     (input) INTEGER                                               */
/*          The leading dimension of the array B. LDB >= max(1,N).        */
/*                                                                        */
/*  ALPHAR  (output) DOUBLE PRECISION array, dimension (N)                */
/*  ALPHAI  (output) DOUBLE PRECISION array, dimension (N)                */
/*  BETA    (output) DOUBLE PRECISION array, dimension (N)                */
/*          On exit, (ALPHAR(j) + ALPHAI(j)*i)/BETA(j), j=1,...,N, will   */
/*          be the generalized eigenvalues.  ALPHAR(j) + ALPHAI(j)*i      */
/*          and BETA(j),j=1,...,N  are the diagonals of the complex Schur */
/*          form (S,T) that would result if the 2-by-2 diagonal blocks of */
/*          the real generalized Schur form of (A,B) were further reduced */
/*          to triangular form using complex unitary transformations.     */
/*          If ALPHAI(j) is zero, then the j-th eigenvalue is real; if    */
/*          positive, then the j-th and (j+1)-st eigenvalues are a        */
/*          complex conjugate pair, with ALPHAI(j+1) negative.            */
/*                                                                        */
/*  Q       (input/output) DOUBLE PRECISION array, dimension (LDQ,N)      */
/*          On entry, if WANTQ = .TRUE., Q is an N-by-N matrix.           */
/*          On exit, Q has been postmultiplied by the left orthogonal     */
/*          transformation matrix which reorder (A, B); The leading M     */
/*          columns of Q form orthonormal bases for the specified pair of */
/*          left eigenspaces (deflating subspaces).                       */
/*          If WANTQ = .FALSE., Q is not referenced.                      */
/*                                                                        */
/*  LDQ     (input) INTEGER                                               */
/*          The leading dimension of the array Q.  LDQ >= 1;              */
/*          and if WANTQ = .TRUE., LDQ >= N.                              */
/*                                                                        */
/*  Z       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)      */
/*          On entry, if WANTZ = .TRUE., Z is an N-by-N matrix.           */
/*          On exit, Z has been postmultiplied by the left orthogonal     */
/*          transformation matrix which reorder (A, B); The leading M     */
/*          columns of Z form orthonormal bases for the specified pair of */
/*          left eigenspaces (deflating subspaces).                       */
/*          If WANTZ = .FALSE., Z is not referenced.                      */
/*                                                                        */
/*  LDZ     (input) INTEGER                                               */
/*          The leading dimension of the array Z. LDZ >= 1;               */
/*          If WANTZ = .TRUE., LDZ >= N.                                  */
/*                                                                        */
/*  M       (output) INTEGER                                              */
/*          The dimension of the specified pair of left and right eigen-  */
/*          spaces (deflating subspaces). 0 <= M <= N.                    */
/*                                                                        */
/*  PL, PR  (output) DOUBLE PRECISION                                     */
/*          If IJOB = 1, 4 or 5, PL, PR are lower bounds on the           */
/*          reciprocal of the norm of "projections" onto left and right   */
/*          eigenspaces with respect to the selected cluster.             */
/*          0 < PL, PR <= 1.                                              */
/*          If M = 0 or M = N, PL = PR  = 1.                              */
/*          If IJOB = 0, 2 or 3, PL and PR are not referenced.            */
/*                                                                        */
/*  DIF     (output) DOUBLE PRECISION array, dimension (2).               */
/*          If IJOB >= 2, DIF(1:2) store the estimates of Difu and Difl.  */
/*          If IJOB = 2 or 4, DIF(1:2) are F-norm-based upper bounds on   */
/*          Difu and Difl. If IJOB = 3 or 5, DIF(1:2) are 1-norm-based    */
/*          estimates of Difu and Difl.                                   */
/*          If M = 0 or N, DIF(1:2) = F-norm([A, B]).                     */
/*          If IJOB = 0 or 1, DIF is not referenced.                      */
/*                                                                        */
/*  WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)  */
/*          IF IJOB = 0, WORK is not referenced.  Otherwise,              */
/*          on exit, if INFO = 0, WORK(1) returns the optimal LWORK.      */
/*                                                                        */
/*  LWORK   (input) INTEGER                                               */
/*          The dimension of the array WORK. LWORK >=  4*N+16.            */
/*          If IJOB = 1, 2 or 4, LWORK >= MAX(4*N+16, 2*M*(N-M)).         */
/*          If IJOB = 3 or 5, LWORK >= MAX(4*N+16, 4*M*(N-M)).            */
/*                                                                        */
/*          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.                 */
/*                                                                        */
/*  IWORK   (workspace/output) INTEGER array, dimension (LIWORK)          */
/*          IF IJOB = 0, IWORK is not referenced.  Otherwise,             */
/*          on exit, if INFO = 0, IWORK(1) returns the optimal LIWORK.    */
/*                                                                        */
/*  LIWORK  (input) INTEGER                                               */
/*          The dimension of the array IWORK. LIWORK >= 1.                */
/*          If IJOB = 1, 2 or 4, LIWORK >=  N+6.                          */
/*          If IJOB = 3 or 5, LIWORK >= MAX(2*M*(N-M), N+6).              */
/*                                                                        */
/*          If LIWORK = -1, then a workspace query is assumed; the        */
/*          routine only calculates the optimal size of the IWORK array,  */
/*          returns this value as the first entry of the IWORK array, and */
/*          no error message related to LIWORK is issued by XERBLA.       */
/*                                                                        */
/*  INFO    (output) INTEGER                                              */
/*            =0: Successful exit.                                        */
/*            <0: If INFO = -i, the i-th argument had an illegal value.   */
/*            =1: Reordering of (A, B) failed because the transformed     */
/*                matrix pair (A, B) would be too far from generalized    */
/*                Schur form; the problem is very ill-conditioned.        */
/*                (A, B) may have been partially reordered.               */
/*                If requested, 0 is returned in DIF(*), PL and PR.       */
/*                                                                        */
/*  Further Details                                                       */
/*  ===============                                                       */
/*                                                                        */
/*  DTGSEN first collects the selected eigenvalues by computing           */
/*  orthogonal U and W that move them to the top left corner of (A, B).   */
/*  In other words, the selected eigenvalues are the eigenvalues of       */
/*  (A11, B11) in:                                                        */
/*                                                                        */
/*                U'*(A, B)*W = (A11 A12) (B11 B12) n1                    */
/*                              ( 0  A22),( 0  B22) n2                    */
/*                                n1  n2    n1  n2                        */
/*                                                                        */
/*  where N = n1+n2 and U' means the transpose of U. The first n1 columns */
/*  of U and W span the specified pair of left and right eigenspaces      */
/*  (deflating subspaces) of (A, B).                                      */
/*                                                                        */
/*  If (A, B) has been obtained from the generalized real Schur           */
/*  decomposition of a matrix pair (C, D) = Q*(A, B)*Z', then the         */
/*  reordered generalized real Schur form of (C, D) is given by           */
/*                                                                        */
/*           (C, D) = (Q*U)*(U'*(A, B)*W)*(Z*W)',                         */
/*                                                                        */
/*  and the first n1 columns of Q*U and Z*W span the corresponding        */
/*  deflating subspaces of (C, D) (Q and Z store Q*U and Z*W, resp.).     */
/*                                                                        */
/*  Note that if the selected eigenvalue is sufficiently ill-conditioned, */
/*  then its value may differ significantly from its value before         */
/*  reordering.                                                           */
/*                                                                        */
/*  The reciprocal condition numbers of the left and right eigenspaces    */
/*  spanned by the first n1 columns of U and W (or Q*U and Z*W) may       */
/*  be returned in DIF(1:2), corresponding to Difu and Difl, resp.        */
/*                                                                        */
/*  The Difu and Difl are defined as:                                     */
/*                                                                        */
/*       Difu[(A11, B11), (A22, B22)] = sigma-min( Zu )                   */
/*  and                                                                   */
/*       Difl[(A11, B11), (A22, B22)] = Difu[(A22, B22), (A11, B11)],     */
/*                                                                        */
/*  where sigma-min(Zu) is the smallest singular value of the             */
/*  (2*n1*n2)-by-(2*n1*n2) matrix                                         */
/*                                                                        */
/*       Zu = [ kron(In2, A11)  -kron(A22', In1) ]                        */
/*            [ kron(In2, B11)  -kron(B22', In1) ].                       */
/*                                                                        */
/*  Here, Inx is the identity matrix of size nx and A22' is the           */
/*  transpose of A22. kron(X, Y) is the Kronecker product between         */
/*  the matrices X and Y.                                                 */
/*                                                                        */
/*  When DIF(2) is small, small changes in (A, B) can cause large changes */
/*  in the deflating subspace. An approximate (asymptotic) bound on the   */
/*  maximum angular error in the computed deflating subspaces is          */
/*                                                                        */
/*       EPS * norm((A, B)) / DIF(2),                                     */
/*                                                                        */
/*  where EPS is the machine precision.                                   */
/*                                                                        */
/*  The reciprocal norm of the projectors on the left and right           */
/*  eigenspaces associated with (A11, B11) may be returned in PL and PR.  */
/*  They are computed as follows. First we compute L and R so that        */
/*  P*(A, B)*Q is block diagonal, where                                   */
/*                                                                        */
/*       P = ( I -L ) n1           Q = ( I R ) n1                         */
/*           ( 0  I ) n2    and        ( 0 I ) n2                         */
/*             n1 n2                    n1 n2                             */
/*                                                                        */
/*  and (L, R) is the solution to the generalized Sylvester equation      */
/*                                                                        */
/*       A11*R - L*A22 = -A12                                             */
/*       B11*R - L*B22 = -B12                                             */
/*                                                                        */
/*  Then PL = (F-norm(L)**2+1)**(-1/2) and PR = (F-norm(R)**2+1)**(-1/2). */
/*  An approximate (asymptotic) bound on the average absolute error of    */
/*  the selected eigenvalues is                                           */
/*                                                                        */
/*       EPS * norm((A, B)) / PL.                                         */
/*                                                                        */
/*  There are also global error bounds which valid for perturbations up   */
/*  to a certain restriction:  A lower bound (x) on the smallest          */
/*  F-norm(E,F) for which an eigenvalue of (A11, B11) may move and        */
/*  coalesce with an eigenvalue of (A22, B22) under perturbation (E,F),   */
/*  (i.e. (A + E, B + F), is                                              */
/*                                                                        */
/*   x = min(Difu,Difl)/((1/(PL*PL)+1/(PR*PR))**(1/2)+2*max(1/PL,1/PR)).  */
/*                                                                        */
/*  An approximate bound on x can be computed from DIF(1:2), PL and PR.   */
/*                                                                        */
/*  If y = ( F-norm(E,F) / x) <= 1, the angles between the perturbed      */
/*  (L', R') and unperturbed (L, R) left and right deflating subspaces    */
/*  associated with the selected cluster in the (1,1)-blocks can be       */
/*  bounded as                                                            */
/*                                                                        */
/*   max-angle(L, L') <= arctan( y * PL / (1 - y * (1 - PL * PL)**(1/2))  */
/*   max-angle(R, R') <= arctan( y * PR / (1 - y * (1 - PR * PR)**(1/2))  */
/*                                                                        */
/*  See LAPACK User's Guide section 4.11 or the following references      */
/*  for more information.                                                 */
/*                                                                        */
/*  Note that if the default method for computing the Frobenius-norm-     */
/*  based estimate DIF is not wanted (see DLATDF), then the parameter     */
/*  IDIFJB (see below) should be changed from 3 to 4 (routine DLATDF      */
/*  (IJOB = 2 will be used)). See DTGSYL for more details.                */
/*                                                                        */
/*  Based on contributions by                                             */
/*     Bo Kagstrom and Peter Poromaa, Department of Computing Science,    */
/*     Umea University, S-901 87 Umea, Sweden.                            */
/*                                                                        */
/*  References                                                            */
/*  ==========                                                            */
/*                                                                        */
/*  [1] B. Kagstrom; A Direct Method for Reordering Eigenvalues in the    */
/*      Generalized Real Schur Form of a Regular Matrix Pair (A, B), in   */
/*      M.S. Moonen et al (eds), Linear Algebra for Large Scale and       */
/*      Real-Time Applications, Kluwer Academic Publ. 1993, pp 195-218.   */
/*                                                                        */
/*  [2] B. Kagstrom and P. Poromaa; Computing Eigenspaces with Specified  */
/*      Eigenvalues of a Regular Matrix Pair (A, B) and Condition         */
/*      Estimation: Theory, Algorithms and Software,                      */
/*      Report UMINF - 94.04, Department of Computing Science, Umea       */
/*      University, S-901 87 Umea, Sweden, 1994. Also as LAPACK Working   */
/*      Note 87. To appear in Numerical Algorithms, 1996.                 */
/*                                                                        */
/*  [3] B. Kagstrom and P. Poromaa, LAPACK-Style Algorithms and Software  */
/*      for Solving the Generalized Sylvester Equation and Estimating the */
/*      Separation between Regular Matrix Pairs, Report UMINF - 93.23,    */
/*      Department of Computing Science, Umea University, S-901 87 Umea,  */
/*      Sweden, December 1993, Revised April 1994, Also as LAPACK Working */
/*      Note 75. To appear in ACM Trans. on Math. Software, Vol 22, No 1, */
/*      1996.                                                             */
/*                                                                        */
/*  ===================================================================== */

    /* Parameter adjustments */
    --select;
    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;
    --alphar;
    --alphai;
    --beta;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1 * 1;
    q -= q_offset;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1 * 1;
    z -= z_offset;
    --dif;
    --work;
    --iwork;

/*     Decode and test the input parameters */

    *info = 0;
    lquery = *lwork == -1 || *liwork == -1;

    if (*ijob < 0 || *ijob > 5) {
        *info = -1;
    } else if (*n < 0) {
        *info = -5;
    } else if (*lda < max(1,*n)) {
        *info = -7;
    } else if (*ldb < max(1,*n)) {
        *info = -9;
    } else if (*ldq < 1 || (*wantq && *ldq < *n)) {
        *info = -14;
    } else if (*ldz < 1 || (*wantz && *ldz < *n)) {
        *info = -16;
    }

    if (*info != 0) {
        i__1 = -(*info);
        xerbla_("DTGSEN", &i__1);
        return;
    }

/*     Get machine constants */

    eps = dlamch_("P");
    smlnum = dlamch_("S") / eps;
    ierr = 0;

    wantp = *ijob == 1 || *ijob >= 4;
    wantd1 = *ijob == 2 || *ijob == 4;
    wantd2 = *ijob == 3 || *ijob == 5;
    wantd = wantd1 || wantd2;

/*     Set M to the dimension of the specified pair of deflating */
/*     subspaces. */

    *m = 0;
    pair = FALSE_;
    for (k = 1; k <= *n; ++k) {
        if (pair) {
            pair = FALSE_;
        } else {
            if (k < *n) {
                if (a[k + 1 + k * a_dim1] == 0.) {
                    if (select[k]) {
                        ++(*m);
                    }
                } else {
                    pair = TRUE_;
                    if (select[k] || select[k + 1]) {
                        *m += 2;
                    }
                }
            } else {
                if (select[*n]) {
                    ++(*m);
                }
            }
        }
    }

    if (*ijob == 1 || *ijob == 2 || *ijob == 4) {
        lwmin  = max(max(1, (*n << 2) + 16), (*m << 1) * (*n - *m));
        liwmin = max(1, *n + 6);
    } else if (*ijob == 3 || *ijob == 5) {
        lwmin  = max(max(1, (*n << 2) + 16), (*m << 2) * (*n - *m));
        liwmin = max(max(1, (*m << 1) * (*n - *m)), *n + 6);
    } else {
        lwmin = max(1,(*n << 2) + 16);
        liwmin = 1;
    }

    work[1] = (doublereal) lwmin;
    iwork[1] = liwmin;

    if (*lwork < lwmin && ! lquery) {
        *info = -22;
    } else if (*liwork < liwmin && ! lquery) {
        *info = -24;
    }

    if (*info != 0) {
        i__1 = -(*info);
        xerbla_("DTGSEN", &i__1);
        return;
    } else if (lquery) {
        return;
    }

/*     Quick return if possible. */

    if (*m == *n || *m == 0) {
        if (wantp) {
            *pl = 1.;
            *pr = 1.;
        }
        if (wantd) {
            dscale = 0.;
            dsum = 1.;
            for (i = 1; i <= *n; ++i) {
                dlassq_(n, &a[i * a_dim1 + 1], &c__1, &dscale, &dsum);
                dlassq_(n, &b[i * b_dim1 + 1], &c__1, &dscale, &dsum);
            }
            dif[1] = dscale * sqrt(dsum);
            dif[2] = dif[1];
        }
        goto L60;
    }

/*     Collect the selected blocks at the top-left corner of (A, B). */

    ks = 0;
    pair = FALSE_;
    for (k = 1; k <= *n; ++k) {
        if (pair) {
            pair = FALSE_;
        } else {

            swap = select[k];
            if (k < *n) {
                if (a[k + 1 + k * a_dim1] != 0.) {
                    pair = TRUE_;
                    swap = swap || select[k + 1];
                }
            }

            if (swap) {
                ++ks;

/*              Swap the K-th block to position KS. */
/*              Perform the reordering of diagonal blocks in (A, B) */
/*              by orthogonal transformation matrices and update */
/*              Q and Z accordingly (if requested): */

                kk = k;
                if (k != ks) {
                    dtgexc_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset],
                            ldb, &q[q_offset], ldq, &z[z_offset], ldz, &kk,
                            &ks, &work[1], lwork, &ierr);
                }

                if (ierr > 0) {

/*                 Swap is rejected: exit. */

                    *info = 1;
                    if (wantp) {
                        *pl = 0.;
                        *pr = 0.;
                    }
                    if (wantd) {
                        dif[1] = 0.;
                        dif[2] = 0.;
                    }
                    goto L60;
                }

                if (pair) {
                    ++ks;
                }
            }
        }
    }
    if (wantp) {

/*        Solve generalized Sylvester equation for R and L */
/*        and compute PL and PR. */

        n1 = *m;
        n2 = *n - *m;
        i = n1 + 1;
        ijb = 0;
        dlacpy_("Full", &n1, &n2, &a[i * a_dim1 + 1], lda, &work[1], &n1);
        dlacpy_("Full", &n1, &n2, &b[i * b_dim1 + 1], ldb, &work[n1 * n2 + 1], &n1);
        i__1 = *lwork - (n1 << 1) * n2;
        dtgsyl_("N", &ijb, &n1, &n2, &a[a_offset], lda, &a[i + i * a_dim1], lda,
                &work[1], &n1, &b[b_offset], ldb, &b[i + i * b_dim1], ldb,
                &work[n1 * n2 + 1], &n1, &dscale, &dif[1],
                &work[(n1 * n2 << 1) + 1], &i__1, &iwork[1], &ierr);

/*        Estimate the reciprocal of norms of "projections" onto left */
/*        and right eigenspaces. */

        rdscal = 0.;
        dsum = 1.;
        i__1 = n1 * n2;
        dlassq_(&i__1, &work[1], &c__1, &rdscal, &dsum);
        *pl = rdscal * sqrt(dsum);
        if (*pl == 0.) {
            *pl = 1.;
        } else {
            *pl = dscale / (sqrt(dscale * dscale / *pl + *pl) * sqrt(*pl));
        }
        rdscal = 0.;
        dsum = 1.;
        i__1 = n1 * n2;
        dlassq_(&i__1, &work[n1 * n2 + 1], &c__1, &rdscal, &dsum);
        *pr = rdscal * sqrt(dsum);
        if (*pr == 0.) {
            *pr = 1.;
        } else {
            *pr = dscale / (sqrt(dscale * dscale / *pr + *pr) * sqrt(*pr));
        }
    }

    if (wantd) {

/*        Compute estimates of Difu and Difl. */

        if (wantd1) {
            n1 = *m;
            n2 = *n - *m;
            i = n1 + 1;
            ijb = 3;

/*           Frobenius norm-based Difu-estimate. */

            i__1 = *lwork - (n1 << 1) * n2;
            dtgsyl_("N", &ijb, &n1, &n2, &a[a_offset], lda, &a[i + i * a_dim1], lda,
                    &work[1], &n1, &b[b_offset], ldb, &b[i + i * b_dim1], ldb,
                    &work[n1 * n2 + 1], &n1, &dscale, &dif[1], &work[(n1 << 1) * n2 + 1],
                    &i__1, &iwork[1], &ierr);

/*           Frobenius norm-based Difl-estimate. */

            i__1 = *lwork - (n1 << 1) * n2;
            dtgsyl_("N", &ijb, &n2, &n1, &a[i + i * a_dim1], lda, &a[a_offset], lda,
                    &work[1], &n2, &b[i + i * b_dim1], ldb, &b[b_offset], ldb,
                    &work[n1 * n2 + 1], &n2, &dscale, &dif[2], &work[(n1 << 1) * n2 + 1],
                    &i__1, &iwork[1], &ierr);
        } else {


/*           Compute 1-norm-based estimates of Difu and Difl using */
/*           reversed communication with DLACON. In each step a */
/*           generalized Sylvester equation or a transposed variant */
/*           is solved. */

            kase = 0;
            n1 = *m;
            n2 = *n - *m;
            i = n1 + 1;
            ijb = 0;
            mn2 = (n1 << 1) * n2;

/*           1-norm-based estimate of Difu. */

L40:
            dlacon_(&mn2, &work[mn2 + 1], &work[1], &iwork[1], &dif[1], &kase);
            if (kase != 0) {
                if (kase == 1) {

/*                 Solve generalized Sylvester equation. */

                    i__1 = *lwork - (n1 << 1) * n2;
                    dtgsyl_("N", &ijb, &n1, &n2, &a[a_offset], lda, &a[i + i * a_dim1], lda,
                            &work[1], &n1, &b[b_offset], ldb, &b[i + i * b_dim1], ldb,
                            &work[n1 * n2 + 1], &n1, &dscale, &dif[1],
                            &work[(n1 << 1) * n2 + 1], &i__1, &iwork[1], &ierr);
                } else {

/*                 Solve the transposed variant. */

                    i__1 = *lwork - (n1 << 1) * n2;
                    dtgsyl_("T", &ijb, &n1, &n2, &a[a_offset], lda, &a[i + i * a_dim1], lda,
                            &work[1], &n1, &b[b_offset], ldb, &b[i + i * b_dim1], ldb,
                            &work[n1 * n2 + 1], &n1, &dscale, &dif[1], &work[(n1 << 1) * n2 + 1],
                            &i__1, &iwork[1], &ierr);
                }
                goto L40;
            }
            dif[1] = dscale / dif[1];

/*           1-norm-based estimate of Difl. */

L50:
            dlacon_(&mn2, &work[mn2 + 1], &work[1], &iwork[1], &dif[2], &kase);
            if (kase != 0) {
                if (kase == 1) {

/*                 Solve generalized Sylvester equation. */

                    i__1 = *lwork - (n1 << 1) * n2;
                    dtgsyl_("N", &ijb, &n2, &n1, &a[i + i * a_dim1], lda, &a[a_offset], lda,
                            &work[1], &n2, &b[i + i * b_dim1], ldb, &b[b_offset], ldb,
                            &work[n1 * n2 + 1], &n2, &dscale, &dif[2],
                            &work[(n1 << 1) * n2 + 1], &i__1, &iwork[1], &ierr);
                } else {

/*                 Solve the transposed variant. */

                    i__1 = *lwork - (n1 << 1) * n2;
                    dtgsyl_("T", &ijb, &n2, &n1, &a[i + i * a_dim1], lda, &a[a_offset], lda,
                            &work[1], &n2, &b[i + i * b_dim1], ldb, &b[b_offset], ldb,
                            &work[n1 * n2 + 1], &n2, &dscale, &dif[2],
                            &work[(n1 << 1) * n2 + 1], &i__1, &iwork[1], &ierr);
                }
                goto L50;
            }
            dif[2] = dscale / dif[2];
        }
    }

L60:

/*     Compute generalized eigenvalues of reordered pair (A, B) and */
/*     normalize the generalized Schur form. */

    pair = FALSE_;
    for (k = 1; k <= *n; ++k) {
        if (pair) {
            pair = FALSE_;
        } else {

            if (k < *n) {
                if (a[k + 1 + k * a_dim1] != 0.) {
                    pair = TRUE_;
                }
            }

            if (pair) {

/*             Compute the eigenvalue(s) at position K. */

                work[1] = a[k + k * a_dim1];
                work[2] = a[k + 1 + k * a_dim1];
                work[3] = a[k + (k + 1) * a_dim1];
                work[4] = a[k + 1 + (k + 1) * a_dim1];
                work[5] = b[k + k * b_dim1];
                work[6] = b[k + 1 + k * b_dim1];
                work[7] = b[k + (k + 1) * b_dim1];
                work[8] = b[k + 1 + (k + 1) * b_dim1];
                d__1 = smlnum * eps;
                dlag2_(&work[1], &c__2, &work[5], &c__2, &d__1,
                       &beta[k], &beta[k + 1], &alphar[k], &alphar[k + 1], &alphai[k]);
                alphai[k + 1] = -alphai[k];

            } else {

                if (d_sign(&c_b28, &b[k + k * b_dim1]) < 0.) {

/*                 If B(K,K) is negative, make it positive */

                    for (i = 1; i <= *n; ++i) {
                        a[k + i * a_dim1] = -a[k + i * a_dim1];
                        b[k + i * b_dim1] = -b[k + i * b_dim1];
                        q[i + k * q_dim1] = -q[i + k * q_dim1];
                    }
                }

                alphar[k] = a[k + k * a_dim1];
                alphai[k] = 0.;
                beta[k] = b[k + k * b_dim1];
            }
        }
    }

    work[1] = (doublereal) lwmin;
    iwork[1] = liwmin;

} /* dtgsen_ */
