*
*
SUBROUTINE PDLAEVSWP( N, ZIN, LDZI, Z, IZ, JZ, DESCZ, NVS, KEY,
$ WORK, LWORK )
*
* -- ScaLAPACK routine (version 1.5) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* April 15, 1997
*
* .. Scalar Arguments ..
INTEGER IZ, JZ, LDZI, LWORK, N
* ..
* .. Array Arguments ..
INTEGER DESCZ( * ), KEY( * ), NVS( * )
DOUBLE PRECISION WORK( * ), Z( * ), ZIN( LDZI, * )
* ..
*
* Purpose
* =======
*
* PDLAEVSWP moves the eigenvectors (potentially unsorted) from
* where they are computed, to a ScaLAPACK standard block cyclic
* array, sorted so that the corresponding eigenvalues are sorted.
*
* 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
* =========
*
* NP = the number of rows local to a given process.
* NQ = the number of columns local to a given process.
*
* N (global input) INTEGER
* The order of the matrix A. N >= 0.
*
* ZIN (local input) DOUBLE PRECISION array,
* dimension ( LDZI, NVS(iam) )
* The eigenvectors on input. Each eigenvector resides entirely
* in one process. Each process holds a contiguous set of
* NVS(iam) eigenvectors. The first eigenvector which the
* process holds is: sum for i=[0,iam-1) of NVS(i)
*
* LDZI (locl input) INTEGER
* leading dimension of the ZIN array
*
* Z (local output) DOUBLE PRECISION array
* global dimension (N, N), local dimension (DESCZ(DLEN_), NQ)
* The eigenvectors on output. The eigenvectors are distributed
* in a block cyclic manner in both dimensions, with a
* block size of NB.
*
* IZ (global input) INTEGER
* Z's global row index, which points to the beginning of the
* submatrix which is to be operated on.
*
* JZ (global input) INTEGER
* Z's global column index, which points to the beginning of
* the submatrix which is to be operated on.
*
* DESCZ (global and local input) INTEGER array of dimension DLEN_.
* The array descriptor for the distributed matrix Z.
*
* NVS (global input) INTEGER array, dimension( nprocs+1 )
* nvs(i) = number of processes
* number of eigenvectors held by processes [0,i-1)
* nvs(1) = number of eigen vectors held by [0,1-1) == 0
* nvs(nprocs+1) = number of eigen vectors held by [0,nprocs) ==
* total number of eigenvectors
*
* KEY (global input) INTEGER array, dimension( N )
* Indicates the actual index (after sorting) for each of the
* eigenvectors.
*
* WORK (local workspace) DOUBLE PRECISION array, dimension (LWORK)
*
* LWORK (local input) INTEGER dimension of WORK
* .. Parameters ..
INTEGER BLOCK_CYCLIC_2D, DLEN_, DTYPE_, CTXT_, M_, N_,
$ MB_, NB_, RSRC_, CSRC_, LLD_
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 CYCLIC_I, CYCLIC_J, DIST, I, IAM, II, INCII, J,
$ MAXI, MAXII, MINI, MINII, MYCOL, MYROW, NB,
$ NBUFSIZE, NPCOL, NPROCS, NPROW, PCOL, RECVCOL,
$ RECVFROM, RECVROW, SENDCOL, SENDROW, SENDTO
* ..
* .. External Functions ..
INTEGER INDXG2L, INDXG2P
EXTERNAL INDXG2L, INDXG2P
* ..
* .. External Subroutines ..
EXTERNAL BLACS_GRIDINFO, DGERV2D, DGESD2D
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX, MIN, MOD
* ..
* .. Executable Statements ..
* This is just to keep ftnchek happy
IF( BLOCK_CYCLIC_2D*CSRC_*CTXT_*DLEN_*DTYPE_*LLD_*MB_*M_*NB_*N_*
$ RSRC_.LT.0 )RETURN
CALL BLACS_GRIDINFO( DESCZ( CTXT_ ), NPROW, NPCOL, MYROW, MYCOL )
IAM = MYROW + MYCOL*NPROW
IAM = MYROW*NPCOL + MYCOL
*
NB = DESCZ( MB_ )
*
NPROCS = NPROW*NPCOL
*
* If PxSTEIN operates on a sub-matrix of a global matrix, the
* key [] that contains the indicies of the eigenvectors is refe-
* renced to the dimensions of the sub-matrix and not the global
* distrubited matrix. Because of this, PxLAEVSWP will incorrectly
* map the eigenvectors to the global eigenvector matrix, Z, unless
* the key[] elements are shifted as below.
*
DO 10 J = DESCZ( N_ ), 1, -1
KEY( J ) = KEY( J-JZ+1 ) + ( JZ-1 )
10 CONTINUE
*
DO 110 DIST = 0, NPROCS - 1
*
SENDTO = MOD( IAM+DIST, NPROCS )
RECVFROM = MOD( NPROCS+IAM-DIST, NPROCS )
*
SENDROW = MOD( SENDTO, NPROW )
SENDCOL = SENDTO / NPROW
RECVROW = MOD( RECVFROM, NPROW )
RECVCOL = RECVFROM / NPROW
*
SENDROW = SENDTO / NPCOL
SENDCOL = MOD( SENDTO, NPCOL )
RECVROW = RECVFROM / NPCOL
RECVCOL = MOD( RECVFROM, NPCOL )
*
* Figure out what I have that process "sendto" wants
*
NBUFSIZE = 0
*
* We are looping through the eigenvectors that I presently own.
*
DO 40 J = NVS( 1+IAM ) + JZ, NVS( 1+IAM+1 ) + JZ - 1
PCOL = INDXG2P( KEY( J ), DESCZ( NB_ ), -1, DESCZ( CSRC_ ),
$ NPCOL )
IF( SENDCOL.EQ.PCOL ) THEN
MINII = MOD( SENDROW+DESCZ( RSRC_ ), NPROW )*
$ DESCZ( MB_ ) + 1
MAXII = DESCZ( M_ )
INCII = DESCZ( MB_ )*NPROW
DO 30 II = MINII, MAXII, INCII
MINI = MAX( II, IZ )
MAXI = MIN( II+DESCZ( MB_ )-1, N+IZ-1 )
DO 20 I = MINI, MAXI, 1
NBUFSIZE = NBUFSIZE + 1
WORK( NBUFSIZE ) = ZIN( I+1-IZ,
$ J-NVS( 1+IAM )+1-JZ )
20 CONTINUE
30 CONTINUE
END IF
40 CONTINUE
*
*
IF( MYROW.NE.SENDROW .OR. MYCOL.NE.SENDCOL )
$ CALL DGESD2D( DESCZ( CTXT_ ), NBUFSIZE, 1, WORK, NBUFSIZE,
$ SENDROW, SENDCOL )
*
*
* Figure out what process "recvfrom" has that I want
*
NBUFSIZE = 0
DO 70 J = NVS( 1+RECVFROM ) + JZ,
$ NVS( 1+RECVFROM+1 ) + JZ - 1, 1
PCOL = INDXG2P( KEY( J ), DESCZ( NB_ ), -1, DESCZ( CSRC_ ),
$ NPCOL )
IF( MYCOL.EQ.PCOL ) THEN
MINII = MOD( MYROW+DESCZ( RSRC_ ), NPROW )*DESCZ( MB_ ) +
$ 1
MAXII = DESCZ( M_ )
INCII = DESCZ( MB_ )*NPROW
DO 60 II = MINII, MAXII, INCII
MINI = MAX( II, IZ )
MAXI = MIN( II+NB-1, N+IZ-1 )
DO 50 I = MINI, MAXI, 1
NBUFSIZE = NBUFSIZE + 1
50 CONTINUE
60 CONTINUE
END IF
70 CONTINUE
*
*
*
IF( MYROW.NE.RECVROW .OR. MYCOL.NE.RECVCOL )
$ CALL DGERV2D( DESCZ( CTXT_ ), 1, NBUFSIZE, WORK, 1, RECVROW,
$ RECVCOL )
*
NBUFSIZE = 0
DO 100 J = NVS( 1+RECVFROM ) + JZ,
$ NVS( 1+RECVFROM+1 ) + JZ - 1, 1
PCOL = INDXG2P( KEY( J ), DESCZ( NB_ ), -1, DESCZ( CSRC_ ),
$ NPCOL )
IF( MYCOL.EQ.PCOL ) THEN
CYCLIC_J = INDXG2L( KEY( J ), DESCZ( MB_ ), -1, -1,
$ NPCOL )
CYCLIC_I = 1
MINII = MOD( MYROW+DESCZ( RSRC_ ), NPROW )*DESCZ( MB_ ) +
$ 1
MAXII = DESCZ( M_ )
INCII = DESCZ( MB_ )*NPROW
DO 90 II = MINII, MAXII, INCII
MINI = MAX( II, IZ )
CYCLIC_I = INDXG2L( MINI, DESCZ( MB_ ), -1, -1,
$ NPROW )
MAXI = MIN( II+NB-1, N+IZ-1 )
DO 80 I = MINI, MAXI, 1
NBUFSIZE = NBUFSIZE + 1
Z( CYCLIC_I+( CYCLIC_J-1 )*DESCZ( LLD_ ) )
$ = WORK( NBUFSIZE )
CYCLIC_I = CYCLIC_I + 1
80 CONTINUE
90 CONTINUE
END IF
100 CONTINUE
*
110 CONTINUE
RETURN
*
* End of PDLAEVSWP
*
END