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Parallel Systems Lecture 10

Parallel Systems Lecture 10. Dr. Guy Tel- Zur. Administration. Home assignments status Final presentation status Open Excel file ps2013a.xlsx Allinea DDT Debugger? Lab #2 will take place on 17/1/13 (lecture #12) @ lab217. Today’s Agenda.

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Parallel Systems Lecture 10

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  1. Parallel SystemsLecture 10 Dr. Guy Tel-Zur

  2. Administration • Home assignments status • Final presentation status • Open Excel file ps2013a.xlsx • Allinea DDT Debugger? • Lab #2 will take place on 17/1/13 (lecture #12) @ lab217

  3. Today’s Agenda • OpenMP examples (SC99 pi integration using Visual Studio). • Openmp_examples.pptx • Combining OpenMP and MPI • hpi.c, hybridpi.c, lecture11-12.pdf • Sorting Algorithms • Wilkinson & Allen chapter 10 • Numerical Algorithms • Wilkinson & Allen chapter 11

  4. Hybrid MPI + OpenMP Demo Machine File: Node1 Node2 Node3 node4 Each node has many cores MPI mpicc -o mpi_outmpi_test.c -fopenmp OpenMP Demo: cd ~/mpi program name: hybridpi.c

  5. Hybrid MPI+OpenMP continued

  6. Hybrid Pi (MPI+OpenMP) #include <stdio.h> #include <mpi.h> #include <omp.h> #define NBIN 100000 #define MAX_THREADS 8 int main(int argc,char **argv) { int nbin,myid,nproc,nthreads,tid; double step,sum[MAX_THREADS]={0.0},pi=0.0,pig; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD,&myid); MPI_Comm_size(MPI_COMM_WORLD,&nproc); nbin = NBIN/nproc; step = 1.0/(nbin*nproc);

  7. #pragma omp parallel private(tid) { int i; double x; nthreads = omp_get_num_threads(); tid = omp_get_thread_num(); for (i=nbin*myid+tid; i<nbin*(myid+1); i+=nthreads) { x = (i+0.5)*step; sum[tid] += 4.0/(1.0+x*x); } printf("rank tid sum = %d %d %e\n",myid,tid,sum[tid]); } for(tid=0; tid<nthreads; tid++) pi += sum[tid]*step; MPI_Allreduce(&pi,&pig,1,MPI_DOUBLE,MPI_SUM,MPI_COMM_WORLD); if (myid==0) printf("PI = %f\n",pig); MPI_Finalize(); return 0; }

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