org.netlib.lapack
Class SLARRE
java.lang.Object
org.netlib.lapack.SLARRE
public class SLARRE
- extends java.lang.Object
SLARRE is a simplified interface to the JLAPACK routine slarre.
This interface converts Java-style 2D row-major arrays into
the 1D column-major 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
* =======
*
* 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 ..
|
Method Summary |
static void |
SLARRE(int n,
float[] d,
float[] e,
float tol,
intW nsplit,
int[] isplit,
intW m,
float[] w,
float[] woff,
float[] gersch,
float[] work,
intW info)
|
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
SLARRE
public SLARRE()
SLARRE
public static void SLARRE(int n,
float[] d,
float[] e,
float tol,
intW nsplit,
int[] isplit,
intW m,
float[] w,
float[] woff,
float[] gersch,
float[] work,
intW info)