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NAME

       PDLACP3  -  i  an  auxiliary routine that copies from a global parallel
       array into a local replicated array or vise versa

SYNOPSIS

       SUBROUTINE PDLACP3( M, I, A, DESCA, B, LDB, II, JJ, REV )

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

           INTEGER         DESCA( * )

           DOUBLE          PRECISION A( * ), B( LDB, * )

PURPOSE

       PDLACP3 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) DOUBLE PRECISION 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) DOUBLE PRECISION 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