org.netlib.lapack
Class DTREXC

java.lang.Object
  org.netlib.lapack.DTREXC

public class DTREXC
extends java.lang.Object

DTREXC is a simplified interface to the JLAPACK routine dtrexc.
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
 *  =======
 *
 *  DTREXC reorders the real Schur factorization of a real matrix
 *  A = Q*T*Q**T, so that the diagonal block of T with row index IFST is

 *  moved to row ILST.
 *
 *  The real Schur form T is reordered by an orthogonal similarity
 *  transformation Z**T*T*Z, and optionally the matrix Q of Schur vectors
 *  is updated by postmultiplying it with Z.
 *
 *  T must be in Schur canonical form (as returned by DHSEQR), that is,
 *  block upper triangular with 1-by-1 and 2-by-2 diagonal blocks; each
 *  2-by-2 diagonal block has its diagonal elements equal and its
 *  off-diagonal elements of opposite sign.
 *
 *  Arguments
 *  =========
 *
 *  COMPQ   (input) CHARACTER*1
 *          = 'V':  update the matrix Q of Schur vectors;
 *          = 'N':  do not update Q.
 *
 *  N       (input) INTEGER
 *          The order of the matrix T. N >= 0.
 *
 *  T       (input/output) DOUBLE PRECISION array, dimension (LDT,N)
 *          On entry, the upper quasi-triangular matrix T, in Schur
 *          Schur canonical form.
 *          On exit, the reordered upper quasi-triangular matrix, again
 *          in Schur canonical form.
 *
 *  LDT     (input) INTEGER
 *          The leading dimension of the array T. LDT >= max(1,N).
 *
 *  Q       (input/output) DOUBLE PRECISION array, dimension (LDQ,N)
 *          On entry, if COMPQ = 'V', the matrix Q of Schur vectors.
 *          On exit, if COMPQ = 'V', Q has been postmultiplied by the
 *          orthogonal transformation matrix Z which reorders T.
 *          If COMPQ = 'N', Q is not referenced.
 *
 *  LDQ     (input) INTEGER
 *          The leading dimension of the array Q.  LDQ >= max(1,N).
 *
 *  IFST    (input/output) INTEGER
 *  ILST    (input/output) INTEGER
 *          Specify the reordering of the diagonal blocks of T.
 *          The block with row index IFST is moved to row ILST, by a
 *          sequence of transpositions 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 <= N; 1 <= ILST <= N.
 *
 *  WORK    (workspace) DOUBLE PRECISION array, dimension (N)
 *
 *  INFO    (output) INTEGER
 *          = 0:  successful exit
 *          < 0:  if INFO = -i, the i-th argument had an illegal value
 *          = 1:  two adjacent blocks were too close to swap (the problem
 *                is very ill-conditioned); T may have been partially
 *                reordered, and ILST points to the first row of the
 *                current position of the block being moved.
 *
 *  =====================================================================
 *
 *     .. Parameters ..

Constructor Summary

DTREXC()

Method Summary

static void

DTREXC(java.lang.String compq, int n, double[][] t, double[][] q, intW ifst, intW ilst, double[] work, intW info)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DTREXC

public DTREXC()

Method Detail

DTREXC

public static void DTREXC(java.lang.String compq,
                          int n,
                          double[][] t,
                          double[][] q,
                          intW ifst,
                          intW ilst,
                          double[] work,
                          intW info)