## org.netlib.lapack Class DLAR1V

```java.lang.Object
org.netlib.lapack.DLAR1V
```

`public class DLAR1Vextends java.lang.Object`

```DLAR1V is a simplified interface to the JLAPACK routine dlar1v.
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
*  =======
*
*  DLAR1V 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) DOUBLE PRECISION
*           The shift. Initially, when R = 0, SIGMA should be a good
*           approximation to an eigenvalue of L D L^T.
*
*  L        (input) DOUBLE PRECISION array, dimension (N-1)
*           The (n-1) subdiagonal elements of the unit bidiagonal matrix
*           L, in elements 1 to N-1.
*
*  D        (input) DOUBLE PRECISION array, dimension (N)
*           The n diagonal elements of the diagonal matrix D.
*
*  LD       (input) DOUBLE PRECISION array, dimension (N-1)
*           The n-1 elements L(i)*D(i).
*
*  LLD      (input) DOUBLE PRECISION array, dimension (N-1)
*           The n-1 elements L(i)*L(i)*D(i).
*
*  GERSCH   (input) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension (N)
*           The (scaled) r-th column of the inverse. Z(R) is returned
*           to be 1.
*
*  ZTZ      (output) DOUBLE PRECISION
*           The square of the norm of Z.
*
*  MINGMA   (output) DOUBLE PRECISION
*           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) DOUBLE PRECISION array, dimension (4*N)
*
*  Further Details
*  ===============
*
*  Based on contributions by
*     Inderjit Dhillon, IBM Almaden, USA
*     Osni Marques, LBNL/NERSC, USA
*
*  =====================================================================
*
*     .. Parameters ..
```

Constructor Summary
`DLAR1V()`

Method Summary
`static void` ```DLAR1V(int n, int b1, int bn, double sigma, double[] d, double[] l, double[] ld, double[] lld, double[] gersch, double[] z, doubleW ztz, doubleW mingma, intW r, int[] isuppz, double[] work)```

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### DLAR1V

`public DLAR1V()`
Method Detail

### DLAR1V

```public static void DLAR1V(int n,
int b1,
int bn,
double sigma,
double[] d,
double[] l,
double[] ld,
double[] lld,
double[] gersch,
double[] z,
doubleW ztz,
doubleW mingma,
intW r,
int[] isuppz,
double[] work)```