NAME

       PSLACP3  -  i  an auxiliary routine that copies from a global parallel  array into a local
       replicated array or vise versa

SYNOPSIS

       SUBROUTINE PSLACP3( M, I, A, DESCA, B, LDB, II, JJ, REV )

           INTEGER         I, II, JJ, LDB, M, REV

           INTEGER         DESCA( * )

           REAL            A( * ), B( LDB, * )

PURPOSE

       PSLACP3 is an auxiliary routine that copies from a global parallel
         array into a local replicated array or vise versa.  Notice that
         the entire submatrix that is copied gets placed on one node or
         more.  The receiving node can be specified precisely, or all nodes
         can receive, or just one row or column of nodes.

       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

       M       (global input) INTEGER
               M is the order of the square submatrix that is copied.  M >= 0.  Unchanged on exit

       I       (global input) INTEGER
               A(I,I) is the global location that the copying starts from.  Unchanged on exit.

       A       (global input/output) REAL array, dimension
               (DESCA(LLD_),*) On entry, the parallel matrix to be copied into or from.  On exit,
               if REV=1, the copied data.  Unchanged on exit if REV=0.

       DESCA   (global and local input) INTEGER array of dimension DLEN_.
               The array descriptor for the distributed matrix A.

       B       (local input/output) REAL array of size (LDB,M)
               If REV=0, this is the global portion of the array A(I:I+M-1,I:I+M-1).   If  REV=1,
               this is the unchanged on exit.

       LDB     (local input) INTEGER
               The leading dimension of B.

       II      (global input) INTEGER
               By using REV 0 & 1, data can be sent out and returned again.  If REV=0, then II is
               destination row index for the node(s) receiving the replicated B.  If II>=0,JJ>=0,
               then  node  (II,JJ)  receives  the data If II=-1,JJ>=0, then all rows in column JJ
               receive the data If II>=0,JJ=-1, then all cols in  row  II  receive  the  data  If
               II=-1,JJ=-1,  then all nodes receive the data If REV<>0, then II is the source row
               index for the node(s) sending the replicated B.

       JJ      (global input) INTEGER
               Similar description as II above

       REV     (global input) INTEGER
               Use REV = 0 to send global A into locally replicated B (on node (II,JJ)).  Use REV
               <>  0  to  send locally replicated B from node (II,JJ) to its owner (which changes
               depending on its location in A) into the global A.

               Implemented by:  G. Henry, May 1, 1997