LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ dlaeda()

subroutine dlaeda ( integer n,
integer tlvls,
integer curlvl,
integer curpbm,
integer, dimension( * ) prmptr,
integer, dimension( * ) perm,
integer, dimension( * ) givptr,
integer, dimension( 2, * ) givcol,
double precision, dimension( 2, * ) givnum,
double precision, dimension( * ) q,
integer, dimension( * ) qptr,
double precision, dimension( * ) z,
double precision, dimension( * ) ztemp,
integer info )

DLAEDA used by DSTEDC. Computes the Z vector determining the rank-one modification of the diagonal matrix. Used when the original matrix is dense.

Download DLAEDA + dependencies [TGZ] [ZIP] [TXT]

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.
!>
Parameters
[in]N
!>          N is INTEGER
!>         The dimension of the symmetric tridiagonal matrix.  N >= 0.
!>
[in]TLVLS
!>          TLVLS is INTEGER
!>         The total number of merging levels in the overall divide and
!>         conquer tree.
!>
[in]CURLVL
!>          CURLVL is INTEGER
!>         The current level in the overall merge routine,
!>         0 <= curlvl <= tlvls.
!>
[in]CURPBM
!>          CURPBM is INTEGER
!>         The current problem in the current level in the overall
!>         merge routine (counting from upper left to lower right).
!>
[in]PRMPTR
!>          PRMPTR is 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.
!>
[in]PERM
!>          PERM is INTEGER array, dimension (N lg N)
!>         Contains the permutations (from deflation and sorting) to be
!>         applied to each eigenblock.
!>
[in]GIVPTR
!>          GIVPTR is 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 rotations.
!>
[in]GIVCOL
!>          GIVCOL is INTEGER array, dimension (2, N lg N)
!>         Each pair of numbers indicates a pair of columns to take place
!>         in a Givens rotation.
!>
[in]GIVNUM
!>          GIVNUM is DOUBLE PRECISION array, dimension (2, N lg N)
!>         Each number indicates the S value to be used in the
!>         corresponding Givens rotation.
!>
[in]Q
!>          Q is DOUBLE PRECISION array, dimension (N**2)
!>         Contains the square eigenblocks from previous levels, the
!>         starting positions for blocks are given by QPTR.
!>
[in]QPTR
!>          QPTR is 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.
!>
[out]Z
!>          Z is 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).
!>
[out]ZTEMP
!>          ZTEMP is DOUBLE PRECISION array, dimension (N)
!>
[out]INFO
!>          INFO is INTEGER
!>          = 0:  successful exit.
!>          < 0:  if INFO = -i, the i-th argument had an illegal value.
!>
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
Jeff Rutter, Computer Science Division, University of California at Berkeley, USA