SUBROUTINE PDLARED2D( N, IA, JA, DESC, BYROW, BYALL, WORK, LWORK )
*
* -- ScaLAPACK routine (version 1.5) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* May 1, 1997
*
* .. Scalar Arguments ..
INTEGER IA, JA, LWORK, N
* ..
* .. Array Arguments ..
INTEGER DESC( * )
DOUBLE PRECISION BYALL( * ), BYROW( * ), WORK( LWORK )
* ..
*
* Purpose
* =======
*
* PDLARED2D redistributes a 1D array
*
* It assumes that the input array, BYROW, is distributed across
* columns and that all process rows contain the same copy of
* BYROW. The output array, BYALL, will be identical on all processes
* 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 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
* =========
*
* NP = Number of local rows in BYROW()
*
* 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 DLEN_
* A 2D array descriptor, which describes BYROW
*
* BYROW (local input) distributed block cyclic DOUBLE PRECISION array
* global dimension (N), local dimension NP
* BYCOL is distributed across the process columns
* All process rows are assumed to contain the same value
*
* BYALL (global output) DOUBLE PRECISION 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) DOUBLE PRECISION dimension (LWORK)
* Used to hold the buffers sent from one process to another
*
* LWORK (local input) INTEGER size of WORK array LWORK >=
* LWORK >= NUMROC(N, DESC( NB_ ), 0, 0, NPCOL)
*
* .. Parameters ..
INTEGER BLOCK_CYCLIC_2D, DLEN_, DTYPE_, CTXT_, M_, N_,
$ MB_, NB_, RSRC_, CSRC_, LLD_
PARAMETER ( BLOCK_CYCLIC_2D = 1, DLEN_ = 9, DTYPE_ = 1,
$ CTXT_ = 2, M_ = 3, N_ = 4, MB_ = 5, NB_ = 6,
$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
* ..
* .. Local Scalars ..
INTEGER ALLI, BUFLEN, I, II, MB, MYCOL, MYROW, NPCOL,
$ NPROW, PROW
* ..
* .. External Functions ..
INTEGER NUMROC
EXTERNAL NUMROC
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDINFO, DCOPY, DGEBR2D, DGEBS2D
* ..
* .. Intrinsic Functions ..
INTRINSIC MIN
* ..
* .. Executable Statements ..
IF( BLOCK_CYCLIC_2D*CSRC_*DLEN_*DTYPE_*LLD_*M_*NB_*N_*RSRC_.LT.0 )
$ RETURN
*
CALL BLACS_GRIDINFO( DESC( CTXT_ ), NPROW, NPCOL, MYROW, MYCOL )
MB = DESC( MB_ )
*
DO 30 PROW = 0, NPROW - 1
BUFLEN = NUMROC( N, MB, PROW, 0, NPROW )
IF( MYROW.EQ.PROW ) THEN
CALL DCOPY( BUFLEN, BYROW, 1, WORK, 1 )
CALL DGEBS2D( DESC( CTXT_ ), 'C', ' ', BUFLEN, 1, WORK,
$ BUFLEN )
ELSE
CALL DGEBR2D( DESC( CTXT_ ), 'C', ' ', BUFLEN, 1, WORK,
$ BUFLEN, PROW, MYCOL )
END IF
*
ALLI = PROW*MB
DO 20 II = 1, BUFLEN, MB
DO 10 I = 1, MIN( MB, BUFLEN-II+1 )
BYALL( ALLI+I ) = WORK( II-1+I )
10 CONTINUE
ALLI = ALLI + MB*NPROW
20 CONTINUE
30 CONTINUE
*
RETURN
END