pslared1d(3)
NAME
PSLARED1D - redistribute a 1D array It assumes that the input array,
BYCOL, is distributed across rows and that all process column contain
the same copy of BYCOL
SYNOPSIS
SUBROUTINE PSLARED1D( N, IA, JA, DESC, BYCOL, BYALL, WORK, LWORK )
INTEGER IA, JA, LWORK, N
INTEGER DESC( * )
REAL BYALL( * ), BYCOL( * ), WORK( LWORK )
PURPOSE
PSLARED1D redistributes a 1D array and will contain the entire array.
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 distributed over. The context itself is global, 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
NP = Number of local rows in BYCOL()
- N (global input) INTEGER
- The number of elements to be redistributed. N >= 0.
- IA (global input) INTEGER
- IA must be equal to 1
- JA (global input) INTEGER
- JA must be equal to 1
- DESC (global/local input) INTEGER Array of dimension 8
- A 2D array descirptor, which describes BYCOL
- BYCOL (local input) distributed block cyclic REAL array
- global dimension (N), local dimension NP BYCOL is distributed across the process rows All process columns are assumed to contain the same value
- BYALL (global output) REAL global dimension( N )
- local dimension (N) BYALL is exactly duplicated on all processes It contains the same values as BYCOL, but it is replicated across all processes rather than being distributed
- BYALL(i) = BYCOL( NUMROC(i,NB,MYROW,0,NPROW ) on the procs whose MYROW == mod((i-1)/NB,NPROW)
- WORK (local workspace) REAL dimension (LWORK)
- Used to hold the buffers sent from one process to another
- LWORK (local input) INTEGER size of WORK array
- LWORK >= NUMROC(N, DESC( NB_ ), 0, 0, NPCOL)