DLAEDA(1) LAPACK routine (version 3.2) DLAEDA(1)NAME
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
SYNOPSIS
SUBROUTINE DLAEDA( N, TLVLS, CURLVL, CURPBM, PRMPTR, PERM, GIVPTR, GIV‐
COL, 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 (counting 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 per‐
mutation and incidentally the size of the full, non-deflated
problem.
PERM (input) INTEGER array, dimension (N lg N)
Contains the permutations (from deflation and sorting) 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 Givens rota‐
tions. 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, dimen‐
sion (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 levels, the start‐
ing 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 eigen‐
block 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 illegal value.
FURTHER DETAILS
Based on contributions by
Jeff Rutter, Computer Science Division, University of California
at Berkeley, USA
LAPACK routine (version 3.2) November 2008 DLAEDA(1)