SRC/slaeda.f(3)

NAME
SRC/slaeda.f

SYNOPSIS

  Functions/Subroutines
subroutine slaeda (n, tlvls, curlvl, curpbm, prmptr, perm, givptr, givcol, givnum, q, qptr, z, ztemp, info)
SLAEDA used by SSTEDC. Computes the Z vector determining the rank-one modification of the diagonal matrix. Used when the original matrix is dense.

Function/Subroutine Documentation

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

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

Purpose:

    !>
    !> SLAEDA 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
    N

    !>          N is INTEGER
    !>         The dimension of the symmetric tridiagonal matrix.  N >= 0.
    !>

    TLVLS

    !>          TLVLS is INTEGER
    !>         The total number of merging levels in the overall divide and
    !>         conquer tree.
    !>

    CURLVL

    !>          CURLVL is INTEGER
    !>         The current level in the overall merge routine,
    !>         0 <= curlvl <= tlvls.
    !>

    CURPBM

    !>          CURPBM is INTEGER
    !>         The current problem in the current level in the overall
    !>         merge routine (counting from upper left to lower right).
    !>

    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.
    !>

    PERM

    !>          PERM is INTEGER array, dimension (N lg N)
    !>         Contains the permutations (from deflation and sorting) to be
    !>         applied to each eigenblock.
    !>

    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.
    !>

    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.
    !>

    GIVNUM

    !>          GIVNUM is REAL array, dimension (2, N lg N)
    !>         Each number indicates the S value to be used in the
    !>         corresponding Givens rotation.
    !>

    Q

    !>          Q is REAL array, dimension (N**2)
    !>         Contains the square eigenblocks from previous levels, the
    !>         starting positions for blocks are given by QPTR.
    !>

    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.
    !>

    Z

    !>          Z is REAL 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

    !>          ZTEMP is REAL array, dimension (N)
    !>

    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

Definition at line 164 of file slaeda.f.

Author

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