NAME
PDLAWIL - get the transform given by H44,H33, & H43H34 into V starting
at row M
SYNOPSIS
SUBROUTINE PDLAWIL( II, JJ, M, A, DESCA, H44, H33, H43H34, V )
INTEGER II, JJ, M
DOUBLE PRECISION H33, H43H34, H44
INTEGER DESCA( * )
DOUBLE PRECISION A( * ), V( * )
PURPOSE
PDLAWIL gets the transform given by H44,H33, & H43H34 into V
starting at row M.
Notes
=====
Each global data object is described by an associated description
vector. This vector stores the information required to establish the
mapping between an object element and its corresponding process and
memory location.
Let A be a generic term for any 2D block cyclicly distributed array.
Such a global array has an associated description vector DESCA. In the
following comments, the character _ should be read as "of the global
array".
NOTATION STORED IN EXPLANATION
--------------- -------------- --------------------------------------
DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
DTYPE_A = 1.
CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
the BLACS process grid A is distribu-
ted over. The context itself is glo-
bal, but the handle (the integer
value) may vary.
M_A (global) DESCA( M_ ) The number of rows in the global
array A.
N_A (global) DESCA( N_ ) The number of columns in the global
array A.
MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
the rows of the array.
NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
the columns of the array.
RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
row of the array A is distributed.
CSRC_A (global) DESCA( CSRC_ ) The process column over which the
first column of the array A is
distributed.
LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
array. LLD_A >= MAX(1,LOCr(M_A)).
Let K be the number of rows or columns of a distributed matrix, and
assume that its process grid has dimension p x q.
LOCr( K ) denotes the number of elements of K that a process would
receive if K were distributed over the p processes of its process
column.
Similarly, LOCc( K ) denotes the number of elements of K that a process
would receive if K were distributed over the q processes of its process
row.
The values of LOCr() and LOCc() may be determined via a call to the
ScaLAPACK tool function, NUMROC:
LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ). An upper
bound for these quantities may be computed by:
LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
ARGUMENTS
II (global input) INTEGER
Row owner of H(M+2,M+2)
JJ (global input) INTEGER
Column owner of H(M+2,M+2)
M (global input) INTEGER
On entry, this is where the transform starts (row M.)
Unchanged on exit.
A (global input) DOUBLE PRECISION array, dimension
(DESCA(LLD_),*) On entry, the Hessenberg matrix. Unchanged on
exit.
DESCA (global and local input) INTEGER array of dimension DLEN_.
The array descriptor for the distributed matrix A. Unchanged
on exit.
H44 H33 H43H34 (global input) DOUBLE PRECISION These three
values are for the double shift QR iteration. Unchanged on
exit.
V (global output) DOUBLE PRECISION array of size 3.
Contains the transform on ouput.
Implemented by: G. Henry, November 17, 1996