org.netlib.arpack
Class Slaqrb

java.lang.Object
  extended by 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 -----------------------------------------------------------------------


Constructor Summary
Slaqrb()
           
 
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
 

Constructor Detail

Slaqrb

public Slaqrb()
Method Detail

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)