org.netlib.lapack
Class Slarre

java.lang.Object
  extended by org.netlib.lapack.Slarre

public class Slarre
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 * ======= * * Given the tridiagonal matrix T, SLARRE sets "small" off-diagonal * elements to zero, and for each unreduced block T_i, it finds * (i) the numbers sigma_i * (ii) the base T_i - sigma_i I = L_i D_i L_i^T representations and * (iii) eigenvalues of each L_i D_i L_i^T. * The representations and eigenvalues found are then used by * SSTEGR to compute the eigenvectors of a symmetric tridiagonal * matrix. Currently, the base representations are limited to being * positive or negative definite, and the eigenvalues of the definite * matrices are found by the dqds algorithm (subroutine SLASQ2). As * an added benefit, SLARRE also outputs the n Gerschgorin * intervals for each L_i D_i L_i^T. * * Arguments * ========= * * N (input) INTEGER * The order of the matrix. * * D (input/output) REAL array, dimension (N) * On entry, the n diagonal elements of the tridiagonal * matrix T. * On exit, the n diagonal elements of the diagonal * matrices D_i. * * E (input/output) REAL array, dimension (N) * On entry, the (n-1) subdiagonal elements of the tridiagonal * matrix T; E(N) need not be set. * On exit, the subdiagonal elements of the unit bidiagonal * matrices L_i. * * TOL (input) REAL * The threshold for splitting. If on input |E(i)| < TOL, then * the matrix T is split into smaller blocks. * * NSPLIT (input) INTEGER * The number of blocks T splits into. 1 <= NSPLIT <= N. * * ISPLIT (output) INTEGER array, dimension (2*N) * The splitting points, at which T breaks up into submatrices. * The first submatrix consists of rows/columns 1 to ISPLIT(1), * the second of rows/columns ISPLIT(1)+1 through ISPLIT(2), * etc., and the NSPLIT-th consists of rows/columns * ISPLIT(NSPLIT-1)+1 through ISPLIT(NSPLIT)=N. * * M (output) INTEGER * The total number of eigenvalues (of all the L_i D_i L_i^T) * found. * * W (output) REAL array, dimension (N) * The first M elements contain the eigenvalues. The * eigenvalues of each of the blocks, L_i D_i L_i^T, are * sorted in ascending order. * * WOFF (output) REAL array, dimension (N) * The NSPLIT base points sigma_i. * * GERSCH (output) REAL array, dimension (2*N) * The n Gerschgorin intervals. * * WORK (input) REAL array, dimension (4*N???) * Workspace. * * INFO (output) INTEGER * Output error code from SLASQ2 * * Further Details * =============== * * Based on contributions by * Inderjit Dhillon, IBM Almaden, USA * Osni Marques, LBNL/NERSC, USA * * ===================================================================== * * .. Parameters ..


Constructor Summary
Slarre()
           
 
Method Summary
static void slarre(int n, float[] d, int _d_offset, float[] e, int _e_offset, float tol, intW nsplit, int[] isplit, int _isplit_offset, intW m, float[] w, int _w_offset, float[] woff, int _woff_offset, float[] gersch, int _gersch_offset, float[] work, int _work_offset, intW info)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Slarre

public Slarre()
Method Detail

slarre

public static void slarre(int n,
                          float[] d,
                          int _d_offset,
                          float[] e,
                          int _e_offset,
                          float tol,
                          intW nsplit,
                          int[] isplit,
                          int _isplit_offset,
                          intW m,
                          float[] w,
                          int _w_offset,
                          float[] woff,
                          int _woff_offset,
                          float[] gersch,
                          int _gersch_offset,
                          float[] work,
                          int _work_offset,
                          intW info)