DLAEDA - compute the Z vector corresponding to the merge
step in the CURLVLth step of the merge process with TLVLS
steps for the CURPBMth problem
SYNOPSIS
SUBROUTINE DLAEDA( N, TLVLS, CURLVL, CURPBM, PRMPTR, PERM,
GIVPTR, GIVCOL, GIVNUM, Q, QPTR, Z,
ZTEMP, INFO )
INTEGER CURLVL, CURPBM, INFO, N, TLVLS
INTEGER GIVCOL( 2, * ), GIVPTR( * ), PERM( * ),
PRMPTR( * ), QPTR( * )
DOUBLE PRECISION GIVNUM( 2, * ), Q( * ), Z( *
), ZTEMP( * )
PURPOSE
DLAEDA computes the Z vector corresponding to the merge
step in the CURLVLth step of the merge process with TLVLS
steps for the CURPBMth problem.
ARGUMENTS
N (input) INTEGER
The dimension of the symmetric tridiagonal matrix.
N >= 0.
TLVLS (input) INTEGER
The total number of merging levels in the overall
divide and conquer tree.
CURLVL (input) INTEGER The current level in the
overall merge routine, 0 <= curlvl <= tlvls.
CURPBM (input) INTEGER The current problem in the
current level in the overall merge routine (count
ing from upper left to lower right).
PRMPTR (input) INTEGER array, dimension (N lg N)
Contains a list of pointers which indicate where in
PERM a level's permutation is stored. PRMPTR(i+1)
- PRMPTR(i) indicates the size of the permutation
and incidentally the size of the full, non-deflated
problem.
PERM (input) INTEGER array, dimension (N lg N)
Contains the permutations (from deflation and sort
ing) to be applied to each eigenblock.
GIVPTR (input) INTEGER array, dimension (N lg N)
Contains a list of pointers which indicate where in
GIVCOL a level's Givens rotations are stored.
GIVPTR(i+1) - GIVPTR(i) indicates the number of
GIVCOL (input) INTEGER array, dimension (2, N lg N)
Each pair of numbers indicates a pair of columns to
take place in a Givens rotation.
GIVNUM (input) DOUBLE PRECISION array, dimension
(2, N lg N) Each number indicates the S value to be
used in the corresponding Givens rotation.
Q (input) DOUBLE PRECISION array, dimension (N**2)
Contains the square eigenblocks from previous lev
els, the starting positions for blocks are given by
QPTR.
QPTR (input) INTEGER array, dimension (N+2)
Contains a list of pointers which indicate where in
Q an eigenblock is stored. SQRT( QPTR(i+1) -
QPTR(i) ) indicates the size of the block.
Z (output) DOUBLE PRECISION array, dimension (N)
On output this vector contains the updating vector
(the last row of the first sub-eigenvector matrix
and the first row of the second sub-eigenvector
matrix).
ZTEMP (workspace) DOUBLE PRECISION array, dimension (N)
INFO (output) INTEGER
= 0: successful exit.
< 0: if INFO = -i, the i-th argument had an ille
gal value.
FURTHER DETAILS
Based on contributions by
Jeff Rutter, Computer Science Division, University of
California
at Berkeley, USA
Man(1) output converted with
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