master-slave-mpi

Master-Slave / Worker-Supervisor Architecture Implemented using Open MPI in C++

About

• This code implements the numerical integration method 'Trapezoidal Rule' to calculate the definite integral over the provided lower and upper limits using Open MPI.

Trapezoidal Rule

• It estimates the integral using the following formula.

 

The greater the number of divisions, the more accurate the estimated calculation of the integral becomes (see the gif below | source: wikipedia)

Calculations

• The looped part of the formula is calculated as per how many divisions you want in your calculation. This workload is divided among the different MPI processes for faster calculation.
• However, in this current implementation, I have not assigned any workload to master or rank 0. It only calculates the end terms and multiplies the result with width.

Running the Code

NOTE: mpiCC -> C++ | mpicc -> C

• The code is based on Open MPI which may be pre-installed on your linux distro.
• Type the following command to see location of the library.

mpiCC --showme

• If not installed, type the following command to install binaries, documentation and lib files of Open MPI.

sudo apt install openmpi-bin openmpi-doc libopenmpi-dev

• Open MPI is generally stored under

/usr/include/x86-64-linux-gnu/

• Make sure the path is included in your includePath as well as path to your binaries.
• Use the following command to compile the MPI code.

mpiCC trap.cpp -o trap.exe

• Use mpirun or mpiexec command to run the code. (here 4 is the number of MPI Process that will execute)

mpirun --hostfile config.txt -np 4 trap.exe

Configuration

• Change the expressions (marked with *** comments) according to the integral you are calculating.
• Please change the config file and replace the IP address with that of your devices in the cluster.
• Set slots as per your need | slots are amount of process that will run on a device.
• Use --oversubscribe to run processes > number of cores.

Issues

• Code gets stuck at MPI_FINALIZE() which I found is a common and recurring issue after some research. Ctrl + C to force exit.

Additional Material

• Use this guide to create cluster with your devices.
• Use this guide to run WSL on your Windows machine to run Unix-based code with VSCode.
• You can contact me for a sequential implementation of the trapzoidal rule that uses of muParser to parse expressions and integrate that into the cluster.