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ScaLAPACK
2.0.2
ScaLAPACK: Scalable Linear Algebra PACKage
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ScaLAPACK
2.0.2
ScaLAPACK: Scalable Linear Algebra PACKage
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#include "../pblas.h"#include "../PBpblas.h"#include "../PBtools.h"#include "../PBblacs.h"#include "../PBblas.h"Go to the source code of this file.
Functions/Subroutines | |
| void | PB_Cdescribe (int M, int N, int IA, int JA, int *DA, int NPROW, int NPCOL, int MYROW, int MYCOL, int *II, int *JJ, int *LDA, int *IMB, int *INB, int *MB, int *NB, int *PROW, int *PCOL, int *DA0) |
| void PB_Cdescribe | ( | int | M, |
| int | N, | ||
| int | IA, | ||
| int | JA, | ||
| int * | DA, | ||
| int | NPROW, | ||
| int | NPCOL, | ||
| int | MYROW, | ||
| int | MYCOL, | ||
| int * | II, | ||
| int * | JJ, | ||
| int * | LDA, | ||
| int * | IMB, | ||
| int * | INB, | ||
| int * | MB, | ||
| int * | NB, | ||
| int * | PROW, | ||
| int * | PCOL, | ||
| int * | DA0 | ||
| ) |
Definition at line 25 of file PB_Cdescribe.c.
{
/*
* Purpose
* =======
*
* PB_Cdescribe returns the global descriptor of a submatrix. This rou-
* tine also computes the starting local index II, JJ corresponding to
* the submatrix starting globally at the entry pointed by IA, JA. This
* routine returns the coordinates in the grid of the process owning the
* matrix entry of global indexes I, J, namely PROW and PCOL. The true
* global block sizes IMB, INB, MB and NB are also returned.
*
* Notes
* =====
*
* A description vector is associated with each 2D block-cyclicly dis-
* tributed matrix. This vector stores the information required to
* establish the mapping between a matrix entry and its corresponding
* process and memory location.
*
* In the following comments, the character _ should be read as
* "of the distributed matrix". Let A be a generic term for any 2D
* block cyclicly distributed matrix. Its description vector is DESC_A:
*
* NOTATION STORED IN EXPLANATION
* ---------------- --------------- ------------------------------------
* DTYPE_A (global) DESCA[ DTYPE_ ] The descriptor type.
* CTXT_A (global) DESCA[ CTXT_ ] The BLACS context handle, indicating
* the NPROW x NPCOL BLACS process grid
* A is distributed over. The context
* itself is global, but the handle
* (the integer value) may vary.
* M_A (global) DESCA[ M_ ] The number of rows in the distribu-
* ted matrix A, M_A >= 0.
* N_A (global) DESCA[ N_ ] The number of columns in the distri-
* buted matrix A, N_A >= 0.
* IMB_A (global) DESCA[ IMB_ ] The number of rows of the upper left
* block of the matrix A, IMB_A > 0.
* INB_A (global) DESCA[ INB_ ] The number of columns of the upper
* left block of the matrix A,
* INB_A > 0.
* MB_A (global) DESCA[ MB_ ] The blocking factor used to distri-
* bute the last M_A-IMB_A rows of A,
* MB_A > 0.
* NB_A (global) DESCA[ NB_ ] The blocking factor used to distri-
* bute the last N_A-INB_A columns of
* A, NB_A > 0.
* RSRC_A (global) DESCA[ RSRC_ ] The process row over which the first
* row of the matrix A is distributed,
* NPROW > RSRC_A >= 0.
* CSRC_A (global) DESCA[ CSRC_ ] The process column over which the
* first column of A is distributed.
* NPCOL > CSRC_A >= 0.
* LLD_A (local) DESCA[ LLD_ ] The leading dimension of the local
* array storing the local blocks of
* the distributed matrix A,
* IF( Lc( 1, N_A ) > 0 )
* LLD_A >= MAX( 1, Lr( 1, M_A ) )
* ELSE
* LLD_A >= 1.
*
* Let K be the number of rows of a matrix A starting at the global in-
* dex IA,i.e, A( IA:IA+K-1, : ). Lr( IA, K ) denotes the number of rows
* that the process of row coordinate MYROW ( 0 <= MYROW < NPROW ) would
* receive if these K rows were distributed over NPROW processes. If K
* is the number of columns of a matrix A starting at the global index
* JA, i.e, A( :, JA:JA+K-1, : ), Lc( JA, K ) denotes the number of co-
* lumns that the process MYCOL ( 0 <= MYCOL < NPCOL ) would receive if
* these K columns were distributed over NPCOL processes.
*
* The values of Lr() and Lc() may be determined via a call to the func-
* tion PB_Cnumroc:
* Lr( IA, K ) = PB_Cnumroc( K, IA, IMB_A, MB_A, MYROW, RSRC_A, NPROW )
* Lc( JA, K ) = PB_Cnumroc( K, JA, INB_A, NB_A, MYCOL, CSRC_A, NPCOL )
*
* Arguments
* =========
*
* M (global input) INTEGER
* On entry, M specifies the number of rows being dealt out
* starting from global index IA. M is also the number of rows
* of the submatrix of interest. M must be at least zero.
*
* N (global input) INTEGER
* On entry, N specifies the number of columns being dealt out
* starting from global index JA. N is also the number of col-
* umns of the submatrix of interest. M must be at least zero.
*
* IA (global input) INTEGER
* On entry, IA specifies the global starting row index of the
* submatrix. IA must at least zero.
*
* JA (global input) INTEGER
* On entry, JA specifies the global starting column index of
* the submatrix. JA must at least zero.
*
* DA (global and local input) INTEGER array
* On entry, DA is an integer array of dimension DLEN_. This is
* the array descriptor of the underlying matrix.
*
* NPROW (global input) INTEGER
* On entry, NPROW specifies the total number of process rows
* over which the matrix is distributed. NPROW must be at least
* one.
*
* NPCOL (global input) INTEGER
* On entry, NPCOL specifies the total number of process columns
* over which the matrix is distributed. NPCOL must be at least
* one.
*
* MYROW (local input) INTEGER
* On entry, MYROW specifies the row coordinate of the process
* whose local index II is determined. MYROW must be at least
* zero and strictly less than NPROW.
*
* II (local output) INTEGER
* On exit, II specifies the local starting row index of the
* submatrix. On exit, II is at least zero.
*
* JJ (local output) INTEGER
* On exit, JJ specifies the local starting column index of the
* submatrix. On exit, JJ is at least zero.
*
* LDA (local output) INTEGER
* On exit, LDA specifies the local leading dimension of the lo-
* cal array containing the distributed matrix entries. LDA must
* be at least one.
*
* IMB (global output) INTEGER
* On exit, IMB specifies the true global number of matrix rows
* of the first block, if M rows are given out starting from the
* global index IA. If M is equal zero, IMB is set to zero.
*
* INB (global output) INTEGER
* On exit, INB specifies the true global number of matrix col-
* umns of the first block, if N columns are given out starting
* from the global index JA. If N is equal zero, INB is set to
* zero.
*
* MB (global output) INTEGER
* On exit, MB specifies the size of the blocks used to parti-
* tion the matrix rows. MB is at least one.
*
* NB (global output) INTEGER
* On exit, NB specifies the size of the blocks used to parti-
* tion the matrix columns. NB is at least one.
*
* PROW (global output) INTEGER
* On exit, PROW specifies the row coordinate of the process
* that possesses the first row of the submatrix. On exit, PROW
* is -1 if DESC( RSRC_ ) is -1 on input, and, at least zero
* and strictly less than NPROW otherwise.
*
* PCOL (global output) INTEGER
* On exit, PCOL specifies the column coordinate of the process
* that possesses the first column of the submatrix. On exit,
* PCOL is -1 if DESC( CSRC_ ) is -1 on input, and, at least
* zero and strictly less than NPCOL otherwise.
*
* DA0 (global and local output) INTEGER array
* On exit, DA0 is an integer array of dimension DLEN_. This is
* the array descriptor of the submatrix A(IA:IA+M-1,JA:JA+N-1).
*
* -- Written on April 1, 1998 by
* Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
*
* ---------------------------------------------------------------------
*/
/* ..
* .. Executable Statements ..
*
*/
*MB = DA[MB_]; Mfirstnb( *IMB, M, IA, DA[IMB_], *MB );
*NB = DA[NB_]; Mfirstnb( *INB, N, JA, DA[INB_], *NB ); *LDA = DA[LLD_];
Minfog2l( IA, JA, DA, NPROW, NPCOL, MYROW, MYCOL, *II, *JJ, *PROW, *PCOL );
MDescSet( DA0, M, N, *IMB, *INB, *MB, *NB, *PROW, *PCOL, DA[CTXT_], *LDA );
/*
* End of PB_Cdescribe
*/
}
