org.netlib.arpack
Class Slaqrb
java.lang.Object
org.netlib.arpack.Slaqrb
public class Slaqrb
- 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.
*-----------------------------------------------------------------------
\BeginDoc
\Name: slaqrb
\Description:
Compute the eigenvalues and the Schur decomposition of an upper
Hessenberg submatrix in rows and columns ILO to IHI. Only the
last component of the Schur vectors are computed.
This is mostly a modification of the LAPACK routine slahqr.
\Usage:
call slaqrb
( WANTT, N, ILO, IHI, H, LDH, WR, WI, Z, INFO )
\Arguments
WANTT Logical variable. (INPUT)
= .TRUE. : the full Schur form T is required;
= .FALSE.: only eigenvalues are required.
N Integer. (INPUT)
The order of the matrix H. N >= 0.
ILO Integer. (INPUT)
IHI Integer. (INPUT)
It is assumed that H is already upper quasi-triangular in
rows and columns IHI+1:N, and that H(ILO,ILO-1) = 0 (unless
ILO = 1). SLAQRB works primarily with the Hessenberg
submatrix in rows and columns ILO to IHI, but applies
transformations to all of H if WANTT is .TRUE..
1 <= ILO <= max(1,IHI); IHI <= N.
H Real array, dimension (LDH,N). (INPUT/OUTPUT)
On entry, the upper Hessenberg matrix H.
On exit, if WANTT is .TRUE., H is upper quasi-triangular in
rows and columns ILO:IHI, with any 2-by-2 diagonal blocks in
standard form. If WANTT is .FALSE., the contents of H are
unspecified on exit.
LDH Integer. (INPUT)
The leading dimension of the array H. LDH >= max(1,N).
WR Real array, dimension (N). (OUTPUT)
WI Real array, dimension (N). (OUTPUT)
The real and imaginary parts, respectively, of the computed
eigenvalues ILO to IHI are stored in the corresponding
elements of WR and WI. If two eigenvalues are computed as a
complex conjugate pair, they are stored in consecutive
elements of WR and WI, say the i-th and (i+1)th, with
WI(i) > 0 and WI(i+1) < 0. If WANTT is .TRUE., 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 2-by-2 diagonal block,
WI(i) = sqrt(H(i+1,i)*H(i,i+1)) and WI(i+1) = -WI(i).
Z Real array, dimension (N). (OUTPUT)
On exit Z contains the last components of the Schur vectors.
INFO Integer. (OUPUT)
= 0: successful exit
> 0: SLAQRB failed to compute all the eigenvalues ILO to IHI
in a total of 30*(IHI-ILO+1) iterations; if INFO = i,
elements i+1:ihi of WR and WI contain those eigenvalues
which have been successfully computed.
\Remarks
1. None.
-----------------------------------------------------------------------
\BeginLib
\Local variables:
xxxxxx real
\Routines called:
slabad LAPACK routine that computes machine constants.
slamch LAPACK routine that determines machine constants.
slanhs LAPACK routine that computes various norms of a matrix.
slanv2 LAPACK routine that computes the Schur factorization of
2 by 2 nonsymmetric matrix in standard form.
slarfg LAPACK Householder reflection construction routine.
scopy Level 1 BLAS that copies one vector to another.
srot Level 1 BLAS that applies a rotation to a 2 by 2 matrix.
\Author
Danny Sorensen Phuong Vu
Richard Lehoucq CRPC / Rice University
Dept. of Computational & Houston, Texas
Applied Mathematics
Rice University
Houston, Texas
\Revision history:
xx/xx/92: Version ' 2.4'
Modified from the LAPACK routine slahqr so that only the
last component of the Schur vectors are computed.
\SCCS Information: @(#)
FILE: laqrb.F SID: 2.2 DATE OF SID: 8/27/96 RELEASE: 2
\Remarks
1. None
\EndLib
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Method Summary |
static void |
slaqrb(boolean wantt,
int n,
int ilo,
int ihi,
float[] h,
int _h_offset,
int ldh,
float[] wr,
int _wr_offset,
float[] wi,
int _wi_offset,
float[] z,
int _z_offset,
org.netlib.util.intW info)
|
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Slaqrb
public Slaqrb()
slaqrb
public static void slaqrb(boolean wantt,
int n,
int ilo,
int ihi,
float[] h,
int _h_offset,
int ldh,
float[] wr,
int _wr_offset,
float[] wi,
int _wi_offset,
float[] z,
int _z_offset,
org.netlib.util.intW info)