NAME

       PSLASWP  - perform a series of row or column interchanges on the distributed matrix sub( A
       ) = A(IA:IA+M-1,JA:JA+N-1)

SYNOPSIS

       SUBROUTINE PSLASWP( DIREC, ROWCOL, N, A, IA, JA, DESCA, K1, K2, IPIV )

           CHARACTER       DIREC, ROWCOL

           INTEGER         IA, JA, K1, K2, N

           INTEGER         DESCA( * ), IPIV( * )

           REAL            A( * )

PURPOSE

       PSLASWP performs a series of row or column interchanges on the distributed matrix sub( A )
       =  A(IA:IA+M-1,JA:JA+N-1).   One  interchange  is initiated for each of rows or columns K1
       trough K2 of sub( A ). This routine assumes that the pivoting information has already been
       broadcast along the process row or column.
       Also  note  that this routine will only work for K1-K2 being in the same MB (or NB) block.
       If you want to pivot a full matrix, use PSLAPIV.

       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

       DIREC   (global input) CHARACTER
               Specifies  in  which  order  the  permutation  is  applied:  = 'F' (Forward) = 'B'
               (Backward)

       ROWCOL  (global input) CHARACTER
               Specifies if the rows or columns are permuted: = 'R' (Rows) = 'C' (Columns)

       N       (global input) INTEGER
               If ROWCOL = 'R', the length of the rows of the distributed  matrix  A(*,JA:JA+N-1)
               to  be  permuted;  If  ROWCOL  = 'C', the length of the columns of the distributed
               matrix A(IA:IA+N-1,*) to be permuted.

       A       (local input/local output) REAL pointer into the
               local memory to an array of dimension (LLD_A, * ).  On entry, this array  contains
               the local pieces of the distri- buted matrix to which the row/columns interchanges
               will be applied. On exit the permuted distributed matrix.

       IA      (global input) INTEGER
               The row index in the global array A indicating the first row of sub( A ).

       JA      (global input) INTEGER
               The column index in the global array A indicating the first column of sub( A ).

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

       K1      (global input) INTEGER
               The first element of IPIV for which a row or column inter- change will be done.

       K2      (global input) INTEGER
               The last element of IPIV for which a row or column inter- change will be done.

       IPIV    (local input) INTEGER array, dimension LOCr(M_A)+MB_A for
               row pivoting and LOCc(N_A)+NB_A for column pivoting.  This array is  tied  to  the
               matrix A, IPIV(K) = L implies rows (or columns) K and L are to be interchanged.