SUBROUTINE PDLASWP( DIREC, ROWCOL, N, A, IA, JA, DESCA, K1, K2, $ IPIV ) * * -- ScaLAPACK auxiliary routine (version 1.5) -- * 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