org.netlib.lapack
Class DHSEQR
java.lang.Object
org.netlib.lapack.DHSEQR
public class DHSEQR
 extends java.lang.Object
DHSEQR is a simplified interface to the JLAPACK routine dhseqr.
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
* =======
*
* DHSEQR computes the eigenvalues of a real upper Hessenberg matrix H
* and, optionally, the matrices T and Z from the Schur decomposition
* H = Z T Z**T, where T is an upper quasitriangular matrix (the Schur
* form), and Z is the orthogonal matrix of Schur vectors.
*
* Optionally Z may be postmultiplied into an input orthogonal matrix Q,
* so that this routine can give the Schur factorization of a matrix A
* which has been reduced to the Hessenberg form H by the orthogonal
* matrix Q: A = Q*H*Q**T = (QZ)*T*(QZ)**T.
*
* Arguments
* =========
*
* JOB (input) CHARACTER*1
* = 'E': compute eigenvalues only;
* = 'S': compute eigenvalues and the Schur form T.
*
* COMPZ (input) CHARACTER*1
* = 'N': no Schur vectors are computed;
* = 'I': Z is initialized to the unit matrix and the matrix Z
* of Schur vectors of H is returned;
* = 'V': Z must contain an orthogonal matrix Q on entry, and
* the product Q*Z is returned.
*
* N (input) INTEGER
* The order of the matrix H. N >= 0.
*
* ILO (input) INTEGER
* IHI (input) INTEGER
* It is assumed that H is already upper triangular in rows
* and columns 1:ILO1 and IHI+1:N. ILO and IHI are normally
* set by a previous call to DGEBAL, and then passed to SGEHRD
* when the matrix output by DGEBAL is reduced to Hessenberg
* form. Otherwise ILO and IHI should be set to 1 and N
* respectively.
* 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
*
* H (input/output) DOUBLE PRECISION array, dimension (LDH,N)
* On entry, the upper Hessenberg matrix H.
* On exit, if JOB = 'S', H contains the upper quasitriangular
* matrix T from the Schur decomposition (the Schur form);
* 2by2 diagonal blocks (corresponding to complex conjugate
* pairs of eigenvalues) are returned in standard form, with
* H(i,i) = H(i+1,i+1) and H(i+1,i)*H(i,i+1) < 0. If JOB = 'E',
* the contents of H are unspecified on exit.
*
* LDH (input) INTEGER
* The leading dimension of the array H. LDH >= max(1,N).
*
* WR (output) DOUBLE PRECISION array, dimension (N)
* WI (output) DOUBLE PRECISION array, dimension (N)
* The real and imaginary parts, respectively, of the computed
* eigenvalues. If two eigenvalues are computed as a complex
* conjugate pair, they are stored in consecutive elements of
* WR and WI, say the ith and (i+1)th, with WI(i) > 0 and
* WI(i+1) < 0. If JOB = 'S', the eigenvalues are stored in the
* same order as on the diagonal of the Schur form returned in
* H, with WR(i) = H(i,i) and, if H(i:i+1,i:i+1) is a 2by2
* diagonal block, WI(i) = sqrt(H(i+1,i)*H(i,i+1)) and
* WI(i+1) = WI(i).
*
* Z (input/output) DOUBLE PRECISION array, dimension (LDZ,N)
* If COMPZ = 'N': Z is not referenced.
* If COMPZ = 'I': on entry, Z need not be set, and on exit, Z
* contains the orthogonal matrix Z of the Schur vectors of H.
* If COMPZ = 'V': on entry Z must contain an NbyN matrix Q,
* which is assumed to be equal to the unit matrix except for
* the submatrix Z(ILO:IHI,ILO:IHI); on exit Z contains Q*Z.
* Normally Q is the orthogonal matrix generated by DORGHR after
* the call to DGEHRD which formed the Hessenberg matrix H.
*
* LDZ (input) INTEGER
* The leading dimension of the array Z.
* LDZ >= max(1,N) if COMPZ = 'I' or 'V'; LDZ >= 1 otherwise.
*
* 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 >= max(1,N).
*
* 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 ith argument had an illegal value
* > 0: if INFO = i, DHSEQR failed to compute all of the
* eigenvalues in a total of 30*(IHIILO+1) iterations;
* elements 1:ilo1 and i+1:n of WR and WI contain those
* eigenvalues which have been successfully computed.
*
* =====================================================================
*
* .. Parameters ..
Method Summary 
static void 
DHSEQR(java.lang.String job,
java.lang.String compz,
int n,
int ilo,
int ihi,
double[][] h,
double[] wr,
double[] wi,
double[][] z,
double[] work,
int lwork,
intW info)

Methods inherited from class java.lang.Object 
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
DHSEQR
public DHSEQR()
DHSEQR
public static void DHSEQR(java.lang.String job,
java.lang.String compz,
int n,
int ilo,
int ihi,
double[][] h,
double[] wr,
double[] wi,
double[][] z,
double[] work,
int lwork,
intW info)