Link to this document's Jupyter Notebook

In order to successfully complete this assignment you need to participate both individually and in groups during class. If you attend class in-person then have one of the instructors check your notebook and sign you out before leaving class on Wednesday March 15.

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In-Class Assignment: MPI Programming Basics

Agenda for today's class (70 minutes)

1. (20 minutes) Pre class Review
2. (30 minutes) Pi Estimation
3. (20 minutes) 1D Array continued

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1. Pre class Review

• 20p--MPI_Syntax_pre-class-assignment

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2. Pi Estimation

Lets go back and consider the pi estimation algorithm we used in 0217-OMP_Threads_in-class-assignment:

#include <omp.h>
static long num_steps = 100000; double step;
#define NUM_THREADS 2
void main ()
{ 
    int i, nthreads; double pi, sum[NUM_THREADS];
     step = 1.0/(double) num_steps;
     omp_set_num_threads(NUM_THREADS);
     #pragma omp parallel
     {
         int i, id,nthrds;
         double x;
         id = omp_get_thread_num();
         nthrds = omp_get_num_threads();
         if (id == 0) nthreads = nthrds;
         for (i=id, sum[id]=0.0;i< num_steps; i=i+nthrds) {
             x = (i+0.5)*step;
             sum[id] += 4.0/(1.0+x*x);
         }
     }
     for(i=0, pi=0.0;i<nthreads;i++)pi += sum[i] * step;
}

✅ DO THIS: As a class, lets discuss the cons for moving this example to a Shared Memory system.

Dispyte this being a poor example for running in MPI, lets spend today converting the code to an MPI version just to get an idea about how MPI would work.

✅ DO THIS: Take the above example and turn it into an MPI Only program.

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3. 1D array continued

For the last few minutes of class we will revisit the 1D array example.

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Congratulations, we're done!

If you attend class in-person then have one of the instructors check your notebook and sign you out before leaving class. If you are attending asynchronously, turn in your assignment using D2L.

Course Resources:

• Website
• ZOOM
• JargonJar
• GIT

Written by Dr. Dirk Colbry, Michigan State University
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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