ScaLAPACK
2.0.2
ScaLAPACK: Scalable Linear Algebra PACKage

#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 blockcyclicly 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_AIMB_A rows of A, * MB_A > 0. * NB_A (global) DESCA[ NB_ ] The blocking factor used to distri * bute the last N_AINB_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+K1, : ). 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+K1, : ), 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+M1,JA:JA+N1). * *  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 */ }