1. Lecture 10
Dr. Guy Tel-Zur

2. Today’s Agenda Sorting Algorithms MatlabMPI demo
Wilkinson & Allen chapter 10OpenMP demo in Visual Studio
MatlabMPI demo
Hybrid OpenMP and MPI programming
hpi.c, hybridpi.c, lecture11-12.pdf
Numerical Algorithms
Wilkinson & Allen chapter 11
CilkPlus (demos in Linux and Visual Studio)
Home assignment #3

3. Visual Studio 2012 express

6. MatlabMPI demo cd to ~/matlab Start Matlab without GUI:
matlab -nojvm –nosplash
If MatMPI directory exists before executing your code then erase it or from inside Matlab type:
MatMPI_Delete_all

7. xbasic.m See more examples : /usr/local/PP/MatlabMPI/examples/
>> MatMPI_Delete_all
No MPI_COMM_WORLD, deleting anyway, files may be leftover.
>> eval(MPI_Run('xbasic',4,{}))
Launching MPI rank: 3 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 2 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 1 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 0 on: hobbit10.ee.bgu.ac.il
unix_launch =
/bin/sh ./MatMPI/Unix_Commands.hobbit10.ee.bgu.ac.il.0.sh &
my_rank: 0
SUCCESS
See more examples : /usr/local/PP/MatlabMPI/examples/

8. hello.m >> MatMPI_Delete_all
>> eval(MPI_Run('hello',4,{}))
Launching MPI rank: 3 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 2 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 1 on: hobbit10.ee.bgu.ac.il
Launching MPI rank: 0 on: hobbit10.ee.bgu.ac.il
unix_launch =
/bin/sh ./MatMPI/Unix_Commands.hobbit10.ee.bgu.ac.il.0.sh &
HelloWorld from rank: 0
SUCCESS

9. Hybrid MPI + OpenMP

11. See helper script: hybrid.bash
Hybrid MPI + OpenMP Demo
Machine File:
Node1
Node2
Node3
node4
Each node has 8 cores
MPI
mpicc -o mpi_out mpi_test.c -fopenmp
See helper script: hybrid.bash
OpenMP
Lecturer's note: make a demo cd ~/mpi program name: hybridpi.c

12. mpicc -o mpi_exe mpi_test.c -fopenmp
export OMP_NUM_THREADS=8
(bash)
mpirun -np 4 –machinefile ./machines mpi_exe
Openmpi extensions (N/A at BGU):
-npersocket, --npersocket <#persocket>On each node, launch this many processes times the number of processor sockets on the node. The -npersocket option also turns on the -bind-to-socket option.-npernode, --npernode <#pernode>On each node, launch this many processes.-pernode, --pernodeOn each node, launch one process -- equivalent to -npernode 1.
-ppn 1

13. Hybrid Pi (MPI+OpenMP)
#include <stdio.h>
#include <mpi.h>
#include <omp.h>
#define NBIN
#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);

14. #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; }

15. Hybrid MPI+OpenMP continued
Lecturer's note:For the demo: See hybrid.bash script