# FreeBSD Manual Pages

PDLARED2D(l) ) PDLARED2D(l)NAMEPDLARED2D - redistribute a 1D array It assumes that the input array, BYROW, is distributed across columns and that all process rows contain the same copy of BYROWSYNOPSISSUBROUTINE PDLARED2D( N, IA, JA, DESC, BYROW, BYALL, WORK, LWORK ) INTEGER IA, JA, LWORK, N INTEGER DESC( * ) DOUBLE PRECISION BYALL( * ), BYROW( * ), WORK( LWORK )PURPOSEPDLARED2D redistributes a 1D array It assumes that the input array, BY- ROW, 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 vec- tor. This vector stores the information required to establish the map- ping 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 as- sume that its process grid has dimension p x q. LOCr( K ) denotes the number of elements of K that a process would re- ceive 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_AARGUMENTSNP = 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 con- tain the same value BYALL (global output) DOUBLE PRECISION global dimension( N ) local dimension (N) BYALL is exactly duplicated on all pro- cesses It contains the same values as BYCOL, but it is repli- cated 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) ScaLAPACK version 1.7 13 August 2001 PDLARED2D(l)

NAME | SYNOPSIS | PURPOSE | ARGUMENTS

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