proc4.cpp File Reference

#include <mpi.h>
#include <vector>

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Macros
#define	DIETAG   2
#define	WORKTAG   1

Functions
static int	clearPending (int numNodes, int myrank, MPI_Request *recvReq, double &tot)
static double	doWork (double *work)
static double *	get_next_work_item (int numCalls)
int	main (int argc, char **argv)

Variables
const int	numEntries = 10
static vector< vector< double > >	recvBuf
const int	totCalls = 2 * 65536

Macro Definition Documentation

#define DIETAG   2

Definition at line 9 of file proc4.cpp.

#define WORKTAG   1

Definition at line 8 of file proc4.cpp.

Function Documentation

static int clearPending ( int  numNodes, int  myrank, MPI_Request *  recvReq, double &  tot  )

static

static double doWork ( double *  work )

static

Definition at line 104 of file proc4.cpp.

References numEntries.

Referenced by main().

{
    double tot = 0;
    for (int i =0; i < numEntries; ++i )
        tot += work[i];
}

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static double* get_next_work_item ( int  numCalls )

static

Definition at line 20 of file proc4.cpp.

References numEntries, and totCalls.

Referenced by main().

{
    static vector< double > ret( numEntries );
    for ( int i = 0; i < numEntries; ++i )
        ret[i] = i + numCalls;

    if ( numCalls >= totCalls )
        return 0;
    return &ret[0];
}

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int main	(	int	argc,
		char **	argv
	)

Definition at line 33 of file proc4.cpp.

References doWork(), get_next_work_item(), numEntries, numNodes, recvBuf, and totCalls.

{
  double tot = 0.0;
  double tc = totCalls;
  double ne = numEntries;
  double expectedTot =
        tc * ( ( ne * (ne - 1.0) )/2.0 ) +
        ne * ( tc * (tc - 1.0) )/2.0;
  int myrank;
  int numNodes;

  /* Initialize MPI */

  MPI_Init(&argc, &argv);

  /* Find out my identity in the default communicator */

  MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
  MPI_Comm_size(MPI_COMM_WORLD, &numNodes);

  double sendBuf[numNodes * numEntries];
  double recvBuf[ numEntries * numNodes ];

  int numCallsPerNode = totCalls / numNodes;

  int begin = myrank * numCallsPerNode;
  int end = begin + numCallsPerNode;

  int k = 0;
  for ( int i = 0; i < numCallsPerNode; ++i ) {
    double* work = get_next_work_item( i + begin );
    int targetNode = i % numNodes;
    for ( int j = 0; j < numEntries; ++j ) {
        sendBuf[targetNode * numEntries + j ] = work[j];
    }

    if ( targetNode == numNodes - 1 ) {
        for ( int j = 0; j < numNodes; ++j ) {
            MPI_Scatter( sendBuf, numEntries, MPI_DOUBLE,
                recvBuf, numEntries * (1 + j ), MPI_DOUBLE, j,
                MPI_COMM_WORLD
            );
            tot += doWork( recvBuf );
        }
    }
  }
  // Final pass to consolidate all the data
  double totBuf[ numNodes ];
  MPI_Allgather( &tot, 1, MPI_DOUBLE,
                  totBuf, 1, MPI_DOUBLE,
                  MPI_COMM_WORLD
               );
  double subtot = tot;
  tot = 0;
  for ( int i = 0; i < numNodes; ++i )
  {
         tot += totBuf[i];
  }

  cout << myrank << ": Tot = " << tot <<
          ", expected = " << expectedTot <<
          ", subtot = " << subtot << endl;

  /* Shut down MPI */

  MPI_Finalize();
  return 0;
}

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Variable Documentation

const int numEntries = 10

Definition at line 14 of file proc4.cpp.

Referenced by doWork(), get_next_work_item(), and main().

vector< vector< double > > recvBuf

static

Definition at line 16 of file proc4.cpp.

Referenced by main().

const int totCalls = 2 * 65536

Definition at line 15 of file proc4.cpp.

Referenced by get_next_work_item(), and main().