org.netlib.lapack
Class Slar1v

java.lang.Object
  extended by org.netlib.lapack.Slar1v

public class Slar1v
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 * ======= * * 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. When sigma is close to an eigenvalue, the * computed vector is an accurate eigenvector. Usually, r corresponds * to the index where the eigenvector is largest in magnitude. * 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. * * LAMBDA (input) REAL * The shift. In order to compute an accurate eigenvector, * LAMBDA 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). * * PIVMIN (input) REAL * The minimum pivot in the Sturm sequence. * * GAPTOL (input) REAL * Tolerance that indicates when eigenvector entries are neglig * w.r.t. their contribution to the residual. * * Z (input/output) REAL array, dimension (N) * On input, all entries of Z must be set to 0. * On output, Z contains the (scaled) r-th column of the * inverse. The scaling is such that Z(R) equals 1. * * WANTNC (input) LOGICAL * Specifies whether NEGCNT has to be computed. * * NEGCNT (output) INTEGER * If WANTNC is .TRUE. then NEGCNT = the number of pivots < piv * in the matrix factorization L D L^T, and NEGCNT = -1 otherw * * ZTZ (output) REAL * The square of the 2-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 * The twist index for the twisted factorization used to * compute Z. * On input, 0 <= R <= N. If R is input as 0, R is set to * the index where (L D L^T - sigma I)^{-1} is largest * in magnitude. If 1 <= R <= N, R is unchanged. * On output, R contains the twist index used to compute Z. * Ideally, R designates the position of the maximum entry in t * eigenvector. * * 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 ). * * NRMINV (output) REAL * NRMINV = 1/SQRT( ZTZ ) * * RESID (output) REAL * The residual of the FP vector. * RESID = ABS( MINGMA )/SQRT( ZTZ ) * * RQCORR (output) REAL * The Rayleigh Quotient correction to LAMBDA. * RQCORR = MINGMA*TMP * * WORK (workspace) REAL array, dimension (4*N) * * Further Details * =============== * * Based on contributions by * Beresford Parlett, University of California, Berkeley, USA * Jim Demmel, University of California, Berkeley, USA * Inderjit Dhillon, University of Texas, Austin, USA * Osni Marques, LBNL/NERSC, USA * Christof Voemel, University of California, Berkeley, USA * * ===================================================================== * * .. Parameters ..


Constructor Summary
Slar1v()
           
 
Method Summary
static void slar1v(int n, int b1, int bn, float lambda, float[] d, int _d_offset, float[] l, int _l_offset, float[] ld, int _ld_offset, float[] lld, int _lld_offset, float pivmin, float gaptol, float[] z, int _z_offset, boolean wantnc, intW negcnt, floatW ztz, floatW mingma, intW r, int[] isuppz, int _isuppz_offset, floatW nrminv, floatW resid, floatW rqcorr, float[] work, int _work_offset)
           
 
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 lambda,
                          float[] d,
                          int _d_offset,
                          float[] l,
                          int _l_offset,
                          float[] ld,
                          int _ld_offset,
                          float[] lld,
                          int _lld_offset,
                          float pivmin,
                          float gaptol,
                          float[] z,
                          int _z_offset,
                          boolean wantnc,
                          intW negcnt,
                          floatW ztz,
                          floatW mingma,
                          intW r,
                          int[] isuppz,
                          int _isuppz_offset,
                          floatW nrminv,
                          floatW resid,
                          floatW rqcorr,
                          float[] work,
                          int _work_offset)