org.netlib.lapack
Class SLASQ2

java.lang.Object
  org.netlib.lapack.SLASQ2

public class SLASQ2
extends java.lang.Object

SLASQ2 is a simplified interface to the JLAPACK routine slasq2.
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
 *  =======
 *
 *  SLASQ2 computes all the eigenvalues of the symmetric positive 
 *  definite tridiagonal matrix associated with the qd array Z to high
 *  relative accuracy are computed to high relative accuracy, in the
 *  absence of denormalization, underflow and overflow.
 *
 *  To see the relation of Z to the tridiagonal matrix, let L be a
 *  unit lower bidiagonal matrix with subdiagonals Z(2,4,6,,..) and
 *  let U be an upper bidiagonal matrix with 1's above and diagonal
 *  Z(1,3,5,,..). The tridiagonal is L*U or, if you prefer, the
 *  symmetric tridiagonal to which it is similar.
 *
 *  Note : SLASQ2 defines a logical variable, IEEE, which is true
 *  on machines which follow ieee-754 floating-point standard in their
 *  handling of infinities and NaNs, and false otherwise. This variable
 *  is passed to SLASQ3.
 *
 *  Arguments
 *  =========
 *
 *  N     (input) INTEGER
 *        The number of rows and columns in the matrix. N >= 0.
 *
 *  Z     (workspace) REAL array, dimension ( 4*N )
 *        On entry Z holds the qd array. On exit, entries 1 to N hold
 *        the eigenvalues in decreasing order, Z( 2*N+1 ) holds the
 *        trace, and Z( 2*N+2 ) holds the sum of the eigenvalues. If
 *        N > 2, then Z( 2*N+3 ) holds the iteration count, Z( 2*N+4 )
 *        holds NDIVS/NIN^2, and Z( 2*N+5 ) holds the percentage of
 *        shifts that failed.
 *
 *  INFO  (output) INTEGER
 *        = 0: successful exit
 *        < 0: if the i-th argument is a scalar and had an illegal
 *             value, then INFO = -i, if the i-th argument is an
 *             array and the j-entry had an illegal value, then
 *             INFO = -(i*100+j)
 *        > 0: the algorithm failed
 *              = 1, a split was marked by a positive value in E
 *              = 2, current block of Z not diagonalized after 30*N
 *                   iterations (in inner while loop)
 *              = 3, termination criterion of outer while loop not met 
 *                   (program created more than N unreduced blocks)
 *
 *  Further Details
 *  ===============
 *  Local Variables: I0:N0 defines a current unreduced segment of Z.
 *  The shifts are accumulated in SIGMA. Iteration count is in ITER.
 *  Ping-pong is controlled by PP (alternates between 0 and 1).
 *
 *  =====================================================================
 *
 *     .. Parameters ..

Constructor Summary

SLASQ2()

Method Summary

static void

SLASQ2(int n, float[] z, intW info)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SLASQ2

public SLASQ2()

Method Detail

SLASQ2

public static void SLASQ2(int n,
                          float[] z,
                          intW info)