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.

LAPACK version 1.5                                 12 May 1997                                        PSLASWP(l)