Parallelrechner

MPI_IRECV(...,request)
...
arrived=FALSE
while (arrived == FALSE) 
{
   "work planned for processor to do while waiting for message data"
   MPI_TEST(request,arrived,status)
}
"work planned for processor to do with the message data"

p = &buffer;
for (i=k; i<k+n; ++i) {
	for(j=l; j<l+m; ++j) {
		*(p++) = a[i][j];
	}
}
MPI_Send(p, n*m, MPI_DOUBLE, dest, tag, MPI_COMM_WORLD)

#include <mpi.h>
void main(int argc, char *argv[]) {
int rank;
double param;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
if(rank==5) param=23.0;
MPI_Bcast(&param,1,MPI_DOUBLE,5,MPI_COMM_WORLD);
printf("P:%d after broadcast parameter is %f \n",rank,param);
MPI_Finalize();
}

#include   <stdio.h>
#include   <mpi.h>
void main(int argc, char *argv[])
{
	int rank;
	int source,result,root;
	/* run on 10 processors */
	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD,&rank);
	root=7;
	source=rank+1;
	MPI_Barrier(MPI_COMM_WORLD);
	MPI_Reduce(&source,&result,1,MPI_INT,MPI_PROD,root,MPI_COMM_WORLD);
	if(rank==root) printf("P:%d MPI_PROD result is %d \n",rank,result);
	MPI_Finalize();
}

#include   <stdio.h>
#include   <mpi.h>
void main(int argc, char *argv[])
{
	int rank,size;
	double param[16],mine;
	int sndcnt,rcvcnt;
	int i;
	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD,&rank);
	MPI_Comm_size(MPI_COMM_WORLD,&size);
	sndcnt=1;
	mine=23.0+rank;
	if(rank==7) rcvcnt=1;
	MPI_Gather(&mine,sndcnt,MPI_DOUBLE,param,rcvcnt,MPI_DOUBLE,7,MPI_COMM_WORLD);
	if(rank==7)
    	for(i=0;i<size;++i) printf("PE:%d param[%d] is %f \n",rank,i,param[i]]); 
	MPI_Finalize();
}

#include <stdio.h>
#include <mpi.h>
void main(int argc, char *argv[]) {
	int rank,size,i;
	double param[8],mine;
	int sndcnt,rcvcnt;
	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD,&rank);
	MPI_Comm_size(MPI_COMM_WORLD,&size);
	rcvcnt=1;
	if(rank==3) {
		for(i=0;i<8;++i) param[i]=23.0+i;
			sndcnt=1;
	}
	MPI_Scatter(param,sndcnt,MPI_DOUBLE,&mine,rcvcnt,MPI_DOUBLE,3,MPI_COMM_WORLD);
	for(i=0;i<size;++i)  {
		if(rank==i) printf("P:%d mine is %f n",rank,mine);
		fflush(stdout);
		MPI_Barrier(MPI_COMM_WORLD);
	}
	MPI_Finalize();
}