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