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## org.netlib.lapack
Class DTGEX2

    java.lang.Object
      org.netlib.lapack.DTGEX2

    public class DTGEX2

extends java.lang.Object

    DTGEX2 is a simplified interface to the JLAPACK routine dtgex2.
    This interface converts Java-style 2D row-major arrays into
    the 1D column-major linearized arrays expected by the lower
    level JLAPACK routines.  Using this interface also allows you
    to omit offset and leading dimension arguments.  However, because
    of these conversions, these routines will be slower than the low
    level ones.  Following is the description from the original Fortran
    source.  Contact seymour@cs.utk.edu with any questions.

     *     ..
     *
     *  Purpose
     *  =======
     *
     *  DTGEX2 swaps adjacent diagonal blocks (A11, B11) and (A22, B22)
     *  of size 1-by-1 or 2-by-2 in an upper (quasi) triangular matrix pair
     *  (A, B) by an orthogonal equivalence transformation.
     *
     *  (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 arrays, dimensions (LDA,N)
     *          On entry, the matrix A in the pair (A, B).
     *          On exit, the updated matrix A.
     *
     *  LDA     (input)  INTEGER
     *          The leading dimension of the array A. LDA >= max(1,N).
     *
     *  B      (input/output) DOUBLE PRECISION arrays, dimensions (LDB,N)
     *          On entry, the matrix B in the pair (A, B).
     *          On exit, the updated matrix 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.
     *          Not referenced if WANTQ = .FALSE..
     *
     *  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.
     *          Not referenced if WANTZ = .FALSE..
     *
     *  LDZ     (input) INTEGER
     *          The leading dimension of the array Z. LDZ >= 1.
     *          If WANTZ = .TRUE., LDZ >= N.
     *
     *  J1      (input) INTEGER
     *          The index to the first block (A11, B11). 1 <= J1 <= N.
     *
     *  N1      (input) INTEGER
     *          The order of the first block (A11, B11). N1 = 0, 1 or 2.
     *
     *  N2      (input) INTEGER
     *          The order of the second block (A22, B22). N2 = 0, 1 or 2.
     *
     *  WORK    (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)).
     *
     *  LWORK   (input) INTEGER
     *          The dimension of the array WORK.
     *          LWORK >=  MAX( 1, N*(N2+N1), (N2+N1)*(N2+N1)*2 )
     *
     *  INFO    (output) INTEGER
     *            =0: Successful exit
     *            >0: If INFO = 1, the transformed matrix (A, B) would be
     *                too far from generalized Schur form; the blocks are
     *                not swapped and (A, B) and (Q, Z) are unchanged.
     *                The problem of swapping is too ill-conditioned.
     *            <0: If INFO = -16: LWORK is too small. Appropriate value
     *                for LWORK is returned in WORK(1).
     *
     *  Further Details
     *  ===============
     *
     *  Based on contributions by
     *     Bo Kagstrom and Peter Poromaa, Department of Computing Science,
     *     Umea University, S-901 87 Umea, Sweden.
     *
     *  In the current code both weak and strong stability tests are
     *  performed. The user can omit the strong stability test by changing
     *  the internal logical parameter WANDS to .FALSE.. See ref. [2] for
     *  details.
     *
     *  [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.
     *
     *  =====================================================================
     *  Replaced various illegal calls to DCOPY by calls to DLASET, or by DO

     *  loops. Sven Hammarling, 1/5/02.
     *
     *     .. Parameters ..

Constructor Summary
`DTGEX2()`

Method Summary
`static void` | `DTGEX2(boolean wantq, boolean wantz, int n, double[][] a, double[][] b, double[][] q, double[][] z, int j1, int n1, int n2, double[] work, int lwork, intW info)`

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

Constructor Detail

### DTGEX2

    public DTGEX2()

Method Detail

### DTGEX2

    public static void DTGEX2(boolean wantq,
                              boolean wantz,
                              int n,
                              double[][] a,
                              double[][] b,
                              double[][] q,
                              double[][] z,
                              int j1,
                              int n1,
                              int n2,
                              double[] work,
                              int lwork,
                              intW info)

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