mirror of https://gitlab.com/QEF/q-e.git
167 lines
6.4 KiB
Fortran
167 lines
6.4 KiB
Fortran
SUBROUTINE INFOG2L( GRINDX, GCINDX, DESC, NPROW, NPCOL, MYROW,
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$ MYCOL, LRINDX, LCINDX, RSRC, CSRC )
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*
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* -- ScaLAPACK tools routine (version 1.5) --
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* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
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* and University of California, Berkeley.
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* May 1, 1997
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*
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* .. Scalar Arguments ..
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INTEGER CSRC, GCINDX, GRINDX, LRINDX, LCINDX, MYCOL,
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$ MYROW, NPCOL, NPROW, RSRC
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* ..
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* .. Array Arguments ..
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INTEGER DESC( * )
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* ..
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*
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* Purpose
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* =======
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*
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* INFOG2L computes the starting local indexes LRINDX, LCINDX corres-
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* ponding to the distributed submatrix starting globally at the entry
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* pointed by GRINDX, GCINDX. This routine returns the coordinates in
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* the grid of the process owning the matrix entry of global indexes
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* GRINDX, GCINDX, namely RSRC and CSRC.
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*
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* Notes
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* =====
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*
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* Each global data object is described by an associated description
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* vector. This vector stores the information required to establish
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* the mapping between an object element and its corresponding process
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* and memory location.
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*
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* Let A be a generic term for any 2D block cyclicly distributed array.
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* Such a global array has an associated description vector DESCA.
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* In the following comments, the character _ should be read as
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* "of the global array".
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*
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* NOTATION STORED IN EXPLANATION
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* --------------- -------------- --------------------------------------
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* DTYPE_A(global) DESCA( DTYPE_ )The descriptor type. In this case,
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* DTYPE_A = 1.
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* CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
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* the BLACS process grid A is distribu-
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* ted over. The context itself is glo-
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* bal, but the handle (the integer
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* value) may vary.
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* M_A (global) DESCA( M_ ) The number of rows in the global
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* array A.
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* N_A (global) DESCA( N_ ) The number of columns in the global
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* array A.
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* MB_A (global) DESCA( MB_ ) The blocking factor used to distribute
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* the rows of the array.
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* NB_A (global) DESCA( NB_ ) The blocking factor used to distribute
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* the columns of the array.
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* RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
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* row of the array A is distributed.
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* CSRC_A (global) DESCA( CSRC_ ) The process column over which the
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* first column of the array A is
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* distributed.
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* LLD_A (local) DESCA( LLD_ ) The leading dimension of the local
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* array. LLD_A >= MAX(1,LOCr(M_A)).
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*
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* Let K be the number of rows or columns of a distributed matrix,
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* and assume that its process grid has dimension p x q.
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* LOCr( K ) denotes the number of elements of K that a process
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* would receive if K were distributed over the p processes of its
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* process column.
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* Similarly, LOCc( K ) denotes the number of elements of K that a
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* process would receive if K were distributed over the q processes of
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* its process row.
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* The values of LOCr() and LOCc() may be determined via a call to the
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* ScaLAPACK tool function, NUMROC:
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* LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
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* LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).
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* An upper bound for these quantities may be computed by:
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* LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
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* LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A
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*
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* Arguments
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* =========
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*
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* GRINDX (global input) INTEGER
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* The global row starting index of the submatrix.
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*
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* GCINDX (global input) INTEGER
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* The global column starting index of the submatrix.
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*
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* DESC (input) INTEGER array of dimension DLEN_.
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* The array descriptor for the underlying distributed matrix.
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*
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* NPROW (global input) INTEGER
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* The total number of process rows over which the distributed
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* matrix is distributed.
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*
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* NPCOL (global input) INTEGER
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* The total number of process columns over which the
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* distributed matrix is distributed.
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*
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* MYROW (local input) INTEGER
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* The row coordinate of the process calling this routine.
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*
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* MYCOL (local input) INTEGER
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* The column coordinate of the process calling this routine.
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*
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* LRINDX (local output) INTEGER
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* The local rows starting index of the submatrix.
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*
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* LCINDX (local output) INTEGER
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* The local columns starting index of the submatrix.
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*
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* RSRC (global output) INTEGER
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* The row coordinate of the process that possesses the first
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* row and column of the submatrix.
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*
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* CSRC (global output) INTEGER
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* The column coordinate of the process that possesses the
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* first row and column of the submatrix.
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*
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* =====================================================================
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*
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* .. Parameters ..
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INTEGER BLOCK_CYCLIC_2D, CSRC_, CTXT_, DLEN_, DTYPE_,
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$ LLD_, MB_, M_, NB_, N_, RSRC_
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PARAMETER ( BLOCK_CYCLIC_2D = 1, DLEN_ = 9, DTYPE_ = 1,
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$ CTXT_ = 2, M_ = 3, N_ = 4, MB_ = 5, NB_ = 6,
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$ RSRC_ = 7, CSRC_ = 8, LLD_ = 9 )
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* ..
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* .. Local Scalars ..
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INTEGER CBLK, GCCPY, GRCPY, RBLK
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MOD
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* ..
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* .. Executable Statements ..
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*
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GRCPY = GRINDX-1
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GCCPY = GCINDX-1
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*
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RBLK = GRCPY / DESC(MB_)
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CBLK = GCCPY / DESC(NB_)
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RSRC = MOD( RBLK + DESC(RSRC_), NPROW )
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CSRC = MOD( CBLK + DESC(CSRC_), NPCOL )
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*
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LRINDX = ( RBLK / NPROW + 1 ) * DESC(MB_) + 1
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LCINDX = ( CBLK / NPCOL + 1 ) * DESC(NB_) + 1
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*
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IF( MOD( MYROW+NPROW-DESC(RSRC_), NPROW ) .GE.
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$ MOD( RBLK, NPROW ) ) THEN
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IF( MYROW.EQ.RSRC )
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$ LRINDX = LRINDX + MOD( GRCPY, DESC(MB_) )
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LRINDX = LRINDX - DESC(MB_)
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END IF
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*
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IF( MOD( MYCOL+NPCOL-DESC(CSRC_), NPCOL ) .GE.
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$ MOD( CBLK, NPCOL ) ) THEN
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IF( MYCOL.EQ.CSRC )
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$ LCINDX = LCINDX + MOD( GCCPY, DESC(NB_) )
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LCINDX = LCINDX - DESC(NB_)
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END IF
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*
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RETURN
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*
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* End of INFOG2L
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*
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END
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