DragonFly On-Line Manual Pages

PSLARED1D(l)                           )                          PSLARED1D(l)

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 It assumes that the input array,
       BYCOL, is distributed across rows and that all process column contain
       the same copy of BYCOL. 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 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)

ScaLAPACK version 1.7           13 August 2001                    PSLARED1D(l)