org.netlib.lapack
Class SLAR1V

java.lang.Object
  extended by org.netlib.lapack.SLAR1V

public class SLAR1V
extends java.lang.Object

SLAR1V is a simplified interface to the JLAPACK routine slar1v.
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 * ======= * * SLAR1V computes the (scaled) r-th column of the inverse of * the sumbmatrix in rows B1 through BN of the tridiagonal matrix * L D L^T - sigma I. The following steps accomplish this computation : * (a) Stationary qd transform, L D L^T - sigma I = L(+) D(+) L(+)^T, * (b) Progressive qd transform, L D L^T - sigma I = U(-) D(-) U(-)^T, * (c) Computation of the diagonal elements of the inverse of * L D L^T - sigma I by combining the above transforms, and choosing * r as the index where the diagonal of the inverse is (one of the) * largest in magnitude. * (d) Computation of the (scaled) r-th column of the inverse using the * twisted factorization obtained by combining the top part of the * the stationary and the bottom part of the progressive transform. * * Arguments * ========= * * N (input) INTEGER * The order of the matrix L D L^T. * * B1 (input) INTEGER * First index of the submatrix of L D L^T. * * BN (input) INTEGER * Last index of the submatrix of L D L^T. * * SIGMA (input) REAL * The shift. Initially, when R = 0, SIGMA should be a good * approximation to an eigenvalue of L D L^T. * * L (input) REAL array, dimension (N-1) * The (n-1) subdiagonal elements of the unit bidiagonal matrix * L, in elements 1 to N-1. * * D (input) REAL array, dimension (N) * The n diagonal elements of the diagonal matrix D. * * LD (input) REAL array, dimension (N-1) * The n-1 elements L(i)*D(i). * * LLD (input) REAL array, dimension (N-1) * The n-1 elements L(i)*L(i)*D(i). * * GERSCH (input) REAL array, dimension (2*N) * The n Gerschgorin intervals. These are used to restrict * the initial search for R, when R is input as 0. * * Z (output) REAL array, dimension (N) * The (scaled) r-th column of the inverse. Z(R) is returned * to be 1. * * ZTZ (output) REAL * The square of the norm of Z. * * MINGMA (output) REAL * The reciprocal of the largest (in magnitude) diagonal * element of the inverse of L D L^T - sigma I. * * R (input/output) INTEGER * Initially, R should be input to be 0 and is then output as * the index where the diagonal element of the inverse is * largest in magnitude. In later iterations, this same value * of R should be input. * * ISUPPZ (output) INTEGER array, dimension (2) * The support of the vector in Z, i.e., the vector Z is * nonzero only in elements ISUPPZ(1) through ISUPPZ( 2 ). * * WORK (workspace) REAL array, dimension (4*N) * * Further Details * =============== * * Based on contributions by * Inderjit Dhillon, IBM Almaden, USA * Osni Marques, LBNL/NERSC, USA * * ===================================================================== * * .. Parameters ..


Constructor Summary
SLAR1V()
           
 
Method Summary
static void SLAR1V(int n, int b1, int bn, float sigma, float[] d, float[] l, float[] ld, float[] lld, float[] gersch, float[] z, floatW ztz, floatW mingma, intW r, int[] isuppz, float[] work)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SLAR1V

public SLAR1V()
Method Detail

SLAR1V

public static void SLAR1V(int n,
                          int b1,
                          int bn,
                          float sigma,
                          float[] d,
                          float[] l,
                          float[] ld,
                          float[] lld,
                          float[] gersch,
                          float[] z,
                          floatW ztz,
                          floatW mingma,
                          intW r,
                          int[] isuppz,
                          float[] work)