Question

Problem 5 (Dot product for multicore machines - 15 points): Complete the SPMD (single pro- gram multiple data) program below for computing dot product on multicore machines using the collective MPI API's listed below. The steps are: compute size, scatter part of vectors x and y to other machines using MPI_Scatter, compute dot product in parallel on all machines and collect partial products using MPI_Gather, add the partial products to come up with a single final product by the master machine. No neeed to initialize the vectors. MPI_Scatter(src_lst,m,MPI_INT,dst_lst,m,MPI_INT,MASTER,world); MPI_Gather(src_buf,number,MPI_INT ,dst_buf,number,MPI_INT,MASTER,world); int main(int argc, char *argv[]) { int i,n,nprocs,pid,size,prod=0; int vector_x[NELMS],vector_y[NELMS),partial_prods[MAXPROCS); MPI_Status status; MPI_Comm world; n= atoi(argv[1]); /* number of elements */ MPI_Init(&argc, &argv); world = MPI_COMM_WORLD; MPI_Comm_size(MPI_COMM_WORLD, &nprocs); MPI_Comm_rank(MPI_COMM_WORLD, &pid); MPI_Finalize(); } int dot_product(int sint e,int *x,int *y){ int i,prod=0; for (i=s;i<e;i++) prod = prod + x[i] * y[i]; return prod; }

Answer 1

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Answer:

MPI_Scatter(src_lst,m,MPI_INT,dst_lst,m,MPI_INT,MASTER,world);

MPI_Gather(src_buf,number,MPI_INT,dst_buf,number,MPI_INT,MASTER,world);

int main(int argc, char *argv[])

{

int i,n,nprocs,pid,size,prod=0;

int vector_x[NELMS],vector_y[NELMS],partial_prods[MAXPROCS];

MPI_Status status;

MPI_Comm world;

n = atoi(argv[1]); /* number of elements */

MPI_Init(&argc, &argv);

world = MPI_COMM_WORLD;

MPI_Comm_size(MPI_COMM_WORLD, &nprocs);

MPI_Comm_rank(MPI_COMM_WORLD, &pid);

size=n/nprocs;

MPI_Scatter(vector_x,size,MPI_INT,partial_prods,m,MPI_INT,MASTER,world);

MPI_Scatter(vector_y,size,MPI_INT,partial_prods,m,MPI_INT,MASTER,world);

prod=dot_product(1,NELMS,vector_x,vector_y);

MPI_Gather(&prod,1,MPI_INT,partial_prods,1,MPI_INT,MASTER,world);

printf("\n DotProduct value is %d",prod);

MPI_Finalize();

}

int dot_product(int s,int e,int *x,int *y)

{

int i,prod=0;

for (i=s;i<=e;i++)

prod=prod+s[i]*y[i];

return prod;

}

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