SUBROUTINE PDLASWP( DIREC, ROWCOL, N, A, IA, JA, DESCA, K1, K2,
$ IPIV )
*
* -- ScaLAPACK auxiliary routine (version 1.7) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* May 1, 1997
*
* .. Scalar Arguments ..
CHARACTER DIREC, ROWCOL
INTEGER IA, JA, K1, K2, N
* ..
* .. Array Arguments ..
INTEGER DESCA( * ), IPIV( * )
DOUBLE PRECISION A( * )
* ..
*
* Purpose:
* ========
*
* PDLASWP 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
* PDLAPIV.
*
* 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) DOUBLE PRECISION 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.
*
* =====================================================================
*
* .. Parameters ..
INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_,
$ LLD_, MB_, M_, NB_, N_, RSRC_
PARAMETER ( BLOCK_CYCLIC_2D = 1, DLEN_ = 9, DTYPE_ = 1,
$ CTXT_ = 2, M_ = 3, N_ = 4, MB_ = 5, NB_ = 6,
$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
* ..
* .. Local Scalars ..
INTEGER I, ICURCOL, ICURROW, IIA, IP, J, JJA, JP,
$ MYCOL, MYROW, NPCOL, NPROW
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDINFO, INFOG2L, PDSWAP
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. Executable Statements ..
*
* Quick return if possible
*
IF( N.EQ.0 )
$ RETURN
*
CALL BLACS_GRIDINFO( DESCA( CTXT_ ), NPROW, NPCOL, MYROW, MYCOL )
*
IF( LSAME( ROWCOL, 'R' ) ) THEN
IF( LSAME( DIREC, 'F' ) ) THEN
CALL INFOG2L( K1, JA, DESCA, NPROW, NPCOL, MYROW, MYCOL,
$ IIA, JJA, ICURROW, ICURCOL )
DO 10 I = K1, K2
IP = IPIV( IIA+I-K1 )
IF( IP.NE.I )
$ CALL PDSWAP( N, A, I, JA, DESCA, DESCA( M_ ), A, IP,
$ JA, DESCA, DESCA( M_ ) )
10 CONTINUE
ELSE
CALL INFOG2L( K2, JA, DESCA, NPROW, NPCOL, MYROW, MYCOL,
$ IIA, JJA, ICURROW, ICURCOL )
DO 20 I = K2, K1, -1
IP = IPIV( IIA+I-K1 )
IF( IP.NE.I )
$ CALL PDSWAP( N, A, I, JA, DESCA, DESCA( M_ ), A, IP,
$ JA, DESCA, DESCA( M_ ) )
20 CONTINUE
END IF
ELSE
IF( LSAME( DIREC, 'F' ) ) THEN
CALL INFOG2L( IA, K1, DESCA, NPROW, NPCOL, MYROW, MYCOL,
$ IIA, JJA, ICURROW, ICURCOL )
DO 30 J = K1, K2
JP = IPIV( JJA+J-K1 )
IF( JP.NE.J )
$ CALL PDSWAP( N, A, IA, J, DESCA, 1, A, IA, JP,
$ DESCA, 1 )
30 CONTINUE
ELSE
CALL INFOG2L( IA, K2, DESCA, NPROW, NPCOL, MYROW, MYCOL,
$ IIA, JJA, ICURROW, ICURCOL )
DO 40 J = K2, K1, -1
JP = IPIV( JJA+J-K1 )
IF( JP.NE.J )
$ CALL PDSWAP( N, A, IA, J, DESCA, 1, A, IA, JP,
$ DESCA, 1 )
40 CONTINUE
END IF
END IF
*
RETURN
*
* End PDLASWP
*
END