org.netlib.lapack
Class SLASD6
java.lang.Object
org.netlib.lapack.SLASD6
public class SLASD6
 extends java.lang.Object
SLASD6 is a simplified interface to the JLAPACK routine slasd6.
This interface converts Javastyle 2D rowmajor arrays into
the 1D columnmajor 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
* =======
*
* SLASD6 computes the SVD of an updated upper bidiagonal matrix B
* obtained by merging two smaller ones by appending a row. This
* routine is used only for the problem which requires all singular
* values and optionally singular vector matrices in factored form.
* B is an NbyM matrix with N = NL + NR + 1 and M = N + SQRE.
* A related subroutine, SLASD1, handles the case in which all singular
* values and singular vectors of the bidiagonal matrix are desired.
*
* SLASD6 computes the SVD as follows:
*
* ( D1(in) 0 0 0 )
* B = U(in) * ( Z1' a Z2' b ) * VT(in)
* ( 0 0 D2(in) 0 )
*
* = U(out) * ( D(out) 0) * VT(out)
*
* where Z' = (Z1' a Z2' b) = u' VT', and u is a vector of dimension M
* with ALPHA and BETA in the NL+1 and NL+2 th entries and zeros
* elsewhere; and the entry b is empty if SQRE = 0.
*
* The singular values of B can be computed using D1, D2, the first
* components of all the right singular vectors of the lower block, and
* the last components of all the right singular vectors of the upper
* block. These components are stored and updated in VF and VL,
* respectively, in SLASD6. Hence U and VT are not explicitly
* referenced.
*
* The singular values are stored in D. The algorithm consists of two
* stages:
*
* The first stage consists of deflating the size of the problem
* when there are multiple singular values or if there is a zero
* in the Z vector. For each such occurence the dimension of the
* secular equation problem is reduced by one. This stage is
* performed by the routine SLASD7.
*
* The second stage consists of calculating the updated
* singular values. This is done by finding the roots of the
* secular equation via the routine SLASD4 (as called by SLASD8).
* This routine also updates VF and VL and computes the distances
* between the updated singular values and the old singular
* values.
*
* SLASD6 is called from SLASDA.
*
* Arguments
* =========
*
* ICOMPQ (input) INTEGER
* Specifies whether singular vectors are to be computed in
* factored form:
* = 0: Compute singular values only.
* = 1: Compute singular vectors in factored form as well.
*
* NL (input) INTEGER
* The row dimension of the upper block. NL >= 1.
*
* NR (input) INTEGER
* The row dimension of the lower block. NR >= 1.
*
* SQRE (input) INTEGER
* = 0: the lower block is an NRbyNR square matrix.
* = 1: the lower block is an NRby(NR+1) rectangular matrix.
*
* The bidiagonal matrix has row dimension N = NL + NR + 1,
* and column dimension M = N + SQRE.
*
* D (input/output) REAL array, dimension ( NL+NR+1 ).
* On entry D(1:NL,1:NL) contains the singular values of the
* upper block, and D(NL+2:N) contains the singular values
* of the lower block. On exit D(1:N) contains the singular
* values of the modified matrix.
*
* VF (input/output) REAL array, dimension ( M )
* On entry, VF(1:NL+1) contains the first components of all
* right singular vectors of the upper block; and VF(NL+2:M)
* contains the first components of all right singular vectors
* of the lower block. On exit, VF contains the first components
* of all right singular vectors of the bidiagonal matrix.
*
* VL (input/output) REAL array, dimension ( M )
* On entry, VL(1:NL+1) contains the last components of all
* right singular vectors of the upper block; and VL(NL+2:M)
* contains the last components of all right singular vectors of
* the lower block. On exit, VL contains the last components of
* all right singular vectors of the bidiagonal matrix.
*
* ALPHA (input) REAL
* Contains the diagonal element associated with the added row.
*
* BETA (input) REAL
* Contains the offdiagonal element associated with the added
* row.
*
* IDXQ (output) INTEGER array, dimension ( N )
* This contains the permutation which will reintegrate the
* subproblem just solved back into sorted order, i.e.
* D( IDXQ( I = 1, N ) ) will be in ascending order.
*
* PERM (output) INTEGER array, dimension ( N )
* The permutations (from deflation and sorting) to be applied
* to each block. Not referenced if ICOMPQ = 0.
*
* GIVPTR (output) INTEGER
* The number of Givens rotations which took place in this
* subproblem. Not referenced if ICOMPQ = 0.
*
* GIVCOL (output) INTEGER array, dimension ( LDGCOL, 2 )
* Each pair of numbers indicates a pair of columns to take place
* in a Givens rotation. Not referenced if ICOMPQ = 0.
*
* LDGCOL (input) INTEGER
* leading dimension of GIVCOL, must be at least N.
*
* GIVNUM (output) REAL array, dimension ( LDGNUM, 2 )
* Each number indicates the C or S value to be used in the
* corresponding Givens rotation. Not referenced if ICOMPQ = 0.
*
* LDGNUM (input) INTEGER
* The leading dimension of GIVNUM and POLES, must be at least N.
*
* POLES (output) REAL array, dimension ( LDGNUM, 2 )
* On exit, POLES(1,*) is an array containing the new singular
* values obtained from solving the secular equation, and
* POLES(2,*) is an array containing the poles in the secular
* equation. Not referenced if ICOMPQ = 0.
*
* DIFL (output) REAL array, dimension ( N )
* On exit, DIFL(I) is the distance between Ith updated
* (undeflated) singular value and the Ith (undeflated) old
* singular value.
*
* DIFR (output) REAL array,
* dimension ( LDGNUM, 2 ) if ICOMPQ = 1 and
* dimension ( N ) if ICOMPQ = 0.
* On exit, DIFR(I, 1) is the distance between Ith updated
* (undeflated) singular value and the I+1th (undeflated) old
* singular value.
*
* If ICOMPQ = 1, DIFR(1:K,2) is an array containing the
* normalizing factors for the right singular vector matrix.
*
* See SLASD8 for details on DIFL and DIFR.
*
* Z (output) REAL array, dimension ( M )
* The first elements of this array contain the components
* of the deflationadjusted updating row vector.
*
* K (output) INTEGER
* Contains the dimension of the nondeflated matrix,
* This is the order of the related secular equation. 1 <= K <=N.
*
* C (output) REAL
* C contains garbage if SQRE =0 and the Cvalue of a Givens
* rotation related to the right null space if SQRE = 1.
*
* S (output) REAL
* S contains garbage if SQRE =0 and the Svalue of a Givens
* rotation related to the right null space if SQRE = 1.
*
* WORK (workspace) REAL array, dimension ( 4 * M )
*
* IWORK (workspace) INTEGER array, dimension ( 3 * N )
*
* INFO (output) INTEGER
* = 0: successful exit.
* < 0: if INFO = i, the ith argument had an illegal value.
* > 0: if INFO = 1, an singular value did not converge
*
* Further Details
* ===============
*
* Based on contributions by
* Ming Gu and Huan Ren, Computer Science Division, University of
* California at Berkeley, USA
*
* =====================================================================
*
* .. Parameters ..
Method Summary 
static void 
SLASD6(int icompq,
int nl,
int nr,
int sqre,
float[] d,
float[] vf,
float[] vl,
floatW alpha,
floatW beta,
int[] idxq,
int[] perm,
intW givptr,
int[][] givcol,
float[][] givnum,
float[][] poles,
float[] difl,
float[] difr,
float[] z,
intW k,
floatW c,
floatW s,
float[] work,
int[] iwork,
intW info)

Methods inherited from class java.lang.Object 
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
SLASD6
public SLASD6()
SLASD6
public static void SLASD6(int icompq,
int nl,
int nr,
int sqre,
float[] d,
float[] vf,
float[] vl,
floatW alpha,
floatW beta,
int[] idxq,
int[] perm,
intW givptr,
int[][] givcol,
float[][] givnum,
float[][] poles,
float[] difl,
float[] difr,
float[] z,
intW k,
floatW c,
floatW s,
float[] work,
int[] iwork,
intW info)