PDLAWIL - get the transform given by H44,H33, & H43H34 into V starting at
- 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( * )
PDLAWIL gets the transform given by H44,H33, & H43H34 into V starting at row
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
N_A (global) DESCA( N_ ) The number of columns in the global
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
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
- 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
- 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