org.netlib.lapack
Class DGGES
java.lang.Object
org.netlib.lapack.DGGES
public class DGGES
 extends java.lang.Object
DGGES is a simplified interface to the JLAPACK routine dgges.
This interface converts Javastyle 2D rowmajor arrays into
the 1D columnmajor 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
* =======
*
* DGGES computes for a pair of NbyN real nonsymmetric matrices (A,B),
* the generalized eigenvalues, the generalized real Schur form (S,T),
* optionally, the left and/or right matrices of Schur vectors (VSL and
* VSR). This gives the generalized Schur factorization
*
* (A,B) = ( (VSL)*S*(VSR)**T, (VSL)*T*(VSR)**T )
*
* Optionally, it also orders the eigenvalues so that a selected cluster
* of eigenvalues appears in the leading diagonal blocks of the upper
* quasitriangular matrix S and the upper triangular matrix T.The
* leading columns of VSL and VSR then form an orthonormal basis for the
* corresponding left and right eigenspaces (deflating subspaces).
*
* (If only the generalized eigenvalues are needed, use the driver
* DGGEV instead, which is faster.)
*
* A generalized eigenvalue for a pair of matrices (A,B) is a scalar w
* or a ratio alpha/beta = w, such that A  w*B is singular. It is
* usually represented as the pair (alpha,beta), as there is a
* reasonable interpretation for beta=0 or both being zero.
*
* A pair of matrices (S,T) is in generalized real Schur form if T is
* upper triangular with nonnegative diagonal and S is block upper
* triangular with 1by1 and 2by2 blocks. 1by1 blocks correspond
* to real generalized eigenvalues, while 2by2 blocks of S will be
* "standardized" by making the corresponding elements of T have the
* form:
* [ a 0 ]
* [ 0 b ]
*
* and the pair of corresponding 2by2 blocks in S and T will have a
* complex conjugate pair of generalized eigenvalues.
*
*
* Arguments
* =========
*
* JOBVSL (input) CHARACTER*1
* = 'N': do not compute the left Schur vectors;
* = 'V': compute the left Schur vectors.
*
* JOBVSR (input) CHARACTER*1
* = 'N': do not compute the right Schur vectors;
* = 'V': compute the right Schur vectors.
*
* SORT (input) CHARACTER*1
* Specifies whether or not to order the eigenvalues on the
* diagonal of the generalized Schur form.
* = 'N': Eigenvalues are not ordered;
* = 'S': Eigenvalues are ordered (see DELZTG);
*
* DELZTG (input) LOGICAL FUNCTION of three DOUBLE PRECISION arguments
* DELZTG must be declared EXTERNAL in the calling subroutine.
* If SORT = 'N', DELZTG is not referenced.
* If SORT = 'S', DELZTG is used to select eigenvalues to sort
* to the top left of the Schur form.
* An eigenvalue (ALPHAR(j)+ALPHAI(j))/BETA(j) is selected if
* DELZTG(ALPHAR(j),ALPHAI(j),BETA(j)) is true; i.e. if either
* one of a complex conjugate pair of eigenvalues is selected,
* then both complex eigenvalues are selected.
*
* Note that in the illconditioned case, a selected complex
* eigenvalue may no longer satisfy DELZTG(ALPHAR(j),ALPHAI(j),
* BETA(j)) = .TRUE. after ordering. INFO is to be set to N+2
* in this case.
*
* N (input) INTEGER
* The order of the matrices A, B, VSL, and VSR. N >= 0.
*
* A (input/output) DOUBLE PRECISION array, dimension (LDA, N)
* On entry, the first of the pair of matrices.
* On exit, A has been overwritten by its generalized Schur
* form S.
*
* LDA (input) INTEGER
* The leading dimension of A. LDA >= max(1,N).
*
* B (input/output) DOUBLE PRECISION array, dimension (LDB, N)
* On entry, the second of the pair of matrices.
* On exit, B has been overwritten by its generalized Schur
* form T.
*
* LDB (input) INTEGER
* The leading dimension of B. LDB >= max(1,N).
*
* SDIM (output) INTEGER
* If SORT = 'N', SDIM = 0.
* If SORT = 'S', SDIM = number of eigenvalues (after sorting)
* for which DELZTG is true. (Complex conjugate pairs for which
* DELZTG is true for either eigenvalue count as 2.)
*
* 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 2by2 diagonal blocks of
* the real Schur form of (A,B) were further reduced to
* triangular form using 2by2 complex unitary transformations.
* If ALPHAI(j) is zero, then the jth eigenvalue is real; if
* positive, then the jth and (j+1)st eigenvalues are a
* complex conjugate pair, with ALPHAI(j+1) negative.
*
* Note: the quotients ALPHAR(j)/BETA(j) and ALPHAI(j)/BETA(j)
* may easily over or underflow, and BETA(j) may even be zero.
* Thus, the user should avoid naively computing the ratio.
* However, ALPHAR and ALPHAI will be always less than and
* usually comparable with norm(A) in magnitude, and BETA always
* less than and usually comparable with norm(B).
*
* VSL (output) DOUBLE PRECISION array, dimension (LDVSL,N)
* If JOBVSL = 'V', VSL will contain the left Schur vectors.
* Not referenced if JOBVSL = 'N'.
*
* LDVSL (input) INTEGER
* The leading dimension of the matrix VSL. LDVSL >=1, and
* if JOBVSL = 'V', LDVSL >= N.
*
* VSR (output) DOUBLE PRECISION array, dimension (LDVSR,N)
* If JOBVSR = 'V', VSR will contain the right Schur vectors.
* Not referenced if JOBVSR = 'N'.
*
* LDVSR (input) INTEGER
* The leading dimension of the matrix VSR. LDVSR >= 1, and
* if JOBVSR = 'V', LDVSR >= N.
*
* WORK (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
* On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
*
* LWORK (input) INTEGER
* The dimension of the array WORK. LWORK >= 8*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.
*
* BWORK (workspace) LOGICAL array, dimension (N)
* Not referenced if SORT = 'N'.
*
* INFO (output) INTEGER
* = 0: successful exit
* < 0: if INFO = i, the ith argument had an illegal value.
* = 1,...,N:
* The QZ iteration failed. (A,B) are not in Schur
* form, but ALPHAR(j), ALPHAI(j), and BETA(j) should
* be correct for j=INFO+1,...,N.
* > N: =N+1: other than QZ iteration failed in DHGEQZ.
* =N+2: after reordering, roundoff changed values of
* some complex eigenvalues so that leading
* eigenvalues in the Generalized Schur form no
* longer satisfy DELZTG=.TRUE. This could also
* be caused due to scaling.
* =N+3: reordering failed in DTGSEN.
*
* =====================================================================
*
* .. Parameters ..
Constructor Summary 
DGGES()

Method Summary 
static void 
DGGES(java.lang.String jobvsl,
java.lang.String jobvsr,
java.lang.String sort,
java.lang.Object delctg,
int n,
double[][] a,
double[][] b,
intW sdim,
double[] alphar,
double[] alphai,
double[] beta,
double[][] vsl,
double[][] vsr,
double[] work,
int lwork,
boolean[] bwork,
intW info)

Methods inherited from class java.lang.Object 
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
DGGES
public DGGES()
DGGES
public static void DGGES(java.lang.String jobvsl,
java.lang.String jobvsr,
java.lang.String sort,
java.lang.Object delctg,
int n,
double[][] a,
double[][] b,
intW sdim,
double[] alphar,
double[] alphai,
double[] beta,
double[][] vsl,
double[][] vsr,
double[] work,
int lwork,
boolean[] bwork,
intW info)