org.netlib.lapack
Class Sgees
java.lang.Object
org.netlib.lapack.Sgees
public class Sgees
- 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
* =======
*
* SGEES computes for an N-by-N real nonsymmetric matrix A, the
* eigenvalues, the real Schur form T, and, optionally, the matrix of
* Schur vectors Z. This gives the Schur factorization A = Z*T*(Z**T).
*
* Optionally, it also orders the eigenvalues on the diagonal of the
* real Schur form so that selected eigenvalues are at the top left.
* The leading columns of Z then form an orthonormal basis for the
* invariant subspace corresponding to the selected eigenvalues.
*
* A matrix is in real Schur form if it is upper quasi-triangular with
* 1-by-1 and 2-by-2 blocks. 2-by-2 blocks will be standardized in the
* form
* [ a b ]
* [ c a ]
*
* where b*c < 0. The eigenvalues of such a block are a +- sqrt(bc).
*
* Arguments
* =========
*
* JOBVS (input) CHARACTER*1
* = 'N': Schur vectors are not computed;
* = 'V': Schur vectors are computed.
*
* SORT (input) CHARACTER*1
* Specifies whether or not to order the eigenvalues on the
* diagonal of the Schur form.
* = 'N': Eigenvalues are not ordered;
* = 'S': Eigenvalues are ordered (see SELECT).
*
* SELECT (input) LOGICAL FUNCTION of two REAL arguments
* SELECT must be declared EXTERNAL in the calling subroutine.
* If SORT = 'S', SELECT is used to select eigenvalues to sort
* to the top left of the Schur form.
* If SORT = 'N', SELECT is not referenced.
* An eigenvalue WR(j)+sqrt(-1)*WI(j) is selected if
* SELECT(WR(j),WI(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 a selected complex eigenvalue may no longer
* satisfy SELECT(WR(j),WI(j)) = .TRUE. after ordering, since
* ordering may change the value of complex eigenvalues
* (especially if the eigenvalue is ill-conditioned); in this
* case INFO is set to N+2 (see INFO below).
*
* N (input) INTEGER
* The order of the matrix A. N >= 0.
*
* A (input/output) REAL array, dimension (LDA,N)
* On entry, the N-by-N matrix A.
* On exit, A has been overwritten by its real Schur form T.
*
* LDA (input) INTEGER
* The leading dimension of the array A. LDA >= max(1,N).
*
* SDIM (output) INTEGER
* If SORT = 'N', SDIM = 0.
* If SORT = 'S', SDIM = number of eigenvalues (after sorting)
* for which SELECT is true. (Complex conjugate
* pairs for which SELECT is true for either
* eigenvalue count as 2.)
*
* WR (output) REAL array, dimension (N)
* WI (output) REAL array, dimension (N)
* WR and WI contain the real and imaginary parts,
* respectively, of the computed eigenvalues in the same order
* that they appear on the diagonal of the output Schur form T.
* Complex conjugate pairs of eigenvalues will appear
* consecutively with the eigenvalue having the positive
* imaginary part first.
*
* VS (output) REAL array, dimension (LDVS,N)
* If JOBVS = 'V', VS contains the orthogonal matrix Z of Schur
* vectors.
* If JOBVS = 'N', VS is not referenced.
*
* LDVS (input) INTEGER
* The leading dimension of the array VS. LDVS >= 1; if
* JOBVS = 'V', LDVS >= N.
*
* WORK (workspace/output) REAL array, dimension (LWORK)
* On exit, if INFO = 0, WORK(1) contains the optimal LWORK.
*
* LWORK (input) INTEGER
* The dimension of the array WORK. LWORK >= max(1,3*N).
* For good performance, LWORK must generally be larger.
*
* 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 i-th argument had an illegal value.
* > 0: if INFO = i, and i is
* <= N: the QR algorithm failed to compute all the
* eigenvalues; elements 1:ILO-1 and i+1:N of WR and WI
* contain those eigenvalues which have converged; if
* JOBVS = 'V', VS contains the matrix which reduces A
* to its partially converged Schur form.
* = N+1: the eigenvalues could not be reordered because some
* eigenvalues were too close to separate (the problem
* is very ill-conditioned);
* = N+2: after reordering, roundoff changed values of some
* complex eigenvalues so that leading eigenvalues in
* the Schur form no longer satisfy SELECT=.TRUE. This
* could also be caused by underflow due to scaling.
*
* =====================================================================
*
* .. Parameters ..
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Constructor Summary |
Sgees()
|
|
Method Summary |
static void |
sgees(java.lang.String jobvs,
java.lang.String sort,
java.lang.Object select,
int n,
float[] a,
int _a_offset,
int lda,
intW sdim,
float[] wr,
int _wr_offset,
float[] wi,
int _wi_offset,
float[] vs,
int _vs_offset,
int ldvs,
float[] work,
int _work_offset,
int lwork,
boolean[] bwork,
int _bwork_offset,
intW info)
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| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Sgees
public Sgees()
sgees
public static void sgees(java.lang.String jobvs,
java.lang.String sort,
java.lang.Object select,
int n,
float[] a,
int _a_offset,
int lda,
intW sdim,
float[] wr,
int _wr_offset,
float[] wi,
int _wi_offset,
float[] vs,
int _vs_offset,
int ldvs,
float[] work,
int _work_offset,
int lwork,
boolean[] bwork,
int _bwork_offset,
intW info)