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## org.netlib.lapack
Class Dtgexc

    java.lang.Object
      org.netlib.lapack.Dtgexc

    public class Dtgexc

extends java.lang.Object

    Following is the description from the original
    Fortran source.  For each array argument, the Java
    version will include an integer offset parameter, so
    the arguments may not match the description exactly.
    Contact seymour@cs.utk.edu with any questions.

     *     ..
     *
     *  Purpose
     *  =======
     *
     *  DTGEXC reorders the generalized real Schur decomposition of a real
     *  matrix pair (A,B) using an orthogonal equivalence transformation
     *
     *                 (A, B) = Q * (A, B) * Z',
     *
     *  so that the diagonal block of (A, B) with row index IFST is moved
     *  to row ILST.
     *
     *  (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.
     *
     *  Optionally, the matrices Q and Z of generalized Schur vectors are
     *  updated.
     *
     *         Q(in) * A(in) * Z(in)' = Q(out) * A(out) * Z(out)'
     *         Q(in) * B(in) * Z(in)' = Q(out) * B(out) * Z(out)'
     *
     *
     *  Arguments
     *  =========
     *
     *  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.
     *
     *  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 matrix A in generalized real Schur canonical
     *          form.
     *          On exit, the updated matrix A, again in generalized
     *          real Schur canonical form.
     *
     *  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 matrix B in generalized real Schur canonical
     *          form (A,B).
     *          On exit, the updated matrix B, again in generalized
     *          real Schur canonical form (A,B).
     *
     *  LDB     (input)  INTEGER
     *          The leading dimension of the array B. LDB >= max(1,N).
     *
     *  Q       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
     *          On entry, if WANTQ = .TRUE., the orthogonal matrix Q.
     *          On exit, the updated matrix Q.
     *          If WANTQ = .FALSE., Q is not referenced.
     *
     *  LDQ     (input) INTEGER
     *          The leading dimension of the array Q. LDQ >= 1.
     *          If WANTQ = .TRUE., LDQ >= N.
     *
     *  Z       (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
     *          On entry, if WANTZ = .TRUE., the orthogonal matrix Z.
     *          On exit, the updated matrix Z.
     *          If WANTZ = .FALSE., Z is not referenced.
     *
     *  LDZ     (input) INTEGER
     *          The leading dimension of the array Z. LDZ >= 1.
     *          If WANTZ = .TRUE., LDZ >= N.
     *
     *  IFST    (input/output) INTEGER
     *  ILST    (input/output) INTEGER
     *          Specify the reordering of the diagonal blocks of (A, B).
     *          The block with row index IFST is moved to row ILST, by a
     *          sequence of swapping between adjacent blocks.
     *          On exit, if IFST pointed on entry to the second row of
     *          a 2-by-2 block, it is changed to point to the first row;
     *          ILST always points to the first row of the block in its
     *          final position (which may differ from its input value by
     *          +1 or -1). 1 <= IFST, ILST <= N.
     *
     *  WORK    (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,L
     *          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
     *
     *  LWORK   (input) INTEGER
     *          The dimension of the array WORK.
     *          LWORK >= 1 when N <= 1, otherwise LWORK >= 4*N + 16.
     *
     *          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.
     *
     *  INFO    (output) INTEGER
     *           =0:  successful exit.
     *           <0:  if INFO = -i, the i-th argument had an illegal value.
     *           =1:  The transformed matrix pair (A, B) would be too far
     *                from generalized Schur form; the problem is ill-
     *                conditioned. (A, B) may have been partially reordered,

     *                and ILST points to the first row of the current
     *                position of the block being moved.
     *
     *  Further Details
     *  ===============
     *
     *  Based on contributions by
     *     Bo Kagstrom and Peter Poromaa, Department of Computing Science,
     *     Umea University, S-901 87 Umea, Sweden.
     *
     *  [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.
     *
     *  =====================================================================
     *
     *     .. Parameters ..

Constructor Summary
`Dtgexc()`

Method Summary
`static void` | `dtgexc(boolean wantq, boolean wantz, int n, double[] a, int _a_offset, int lda, double[] b, int _b_offset, int ldb, double[] q, int _q_offset, int ldq, double[] z, int _z_offset, int ldz, intW ifst, intW ilst, double[] work, int _work_offset, int lwork, intW info)`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### Dtgexc

    public Dtgexc()

Method Detail

### dtgexc

    public static void dtgexc(boolean wantq,
                              boolean wantz,
                              int n,
                              double[] a,
                              int _a_offset,
                              int lda,
                              double[] b,
                              int _b_offset,
                              int ldb,
                              double[] q,
                              int _q_offset,
                              int ldq,
                              double[] z,
                              int _z_offset,
                              int ldz,
                              intW ifst,
                              intW ilst,
                              double[] work,
                              int _work_offset,
                              int lwork,
                              intW info)

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