MPI with Python

This repository demonstrates the use of Message Passing Interface (MPI) in Python using mpi4py. It contains Python scripts that illustrate basic point-to-point communication and environment setup for parallel computing.

Repository Structure

• point-to-point.py: A Python script demonstrating point-to-point communication between two MPI processes. Process 0 sends a "Hello, world" message to Process 1, which receives and prints it. The script includes explanatory print statements to guide you through each step of the communication process.

• mpi_test.py: A basic Python script that initializes an MPI communicator and prints a message from each process. It demonstrates how to initialize MPI in Python and verify that multiple processes are running.

• core_count.py: A simple Python script that prints the number of logical cores available on your system. This helps in understanding the number of processes you could potentially run in parallel.

Installation

To run these scripts, you need to have Python, mpi4py, and an MPI implementation (such as Open MPI) installed on your system. Follow the instructions below to set up your environment.

Step 1: Install Python and Create a Virtual Environment

Ensure you have Python 3 installed. Then, create a virtual environment to manage your dependencies:

python3 -m venv myenv
source myenv/bin/activate

Step 2: Install mpi4py

With the virtual environment activated, install mpi4py:

pip install mpi4py

Step 3: Install Open MPI

On macOS, you can install Open MPI using Homebrew:

brew install open-mpi

Configure Open MPI to use TCP for communication by setting the following environment variable:

export OMPI_MCA_btl="self,tcp"

Step 4: Install Dependencies from requirements.txt

pip install -r requirements.txt

Running the Scripts

Running point-to-point.py

To run the point-to-point.py script, use the following command to start two MPI processes:

mpiexec -n 2 python3 point-to-point.py

Expected Output

MPI communicator initialized.
Total number of processes: 2
This process has rank (ID): 0
Process 0 is sending the message: 'Hello, world' to process 1
Process 0 has sent the message to process 1.
MPI communicator initialized.
Total number of processes: 2
This process has rank (ID): 1
Process 1 is waiting to receive a message from process 0.
Process 1 received the message: 'Hello, world' from process 0.

Running mpi_test.py

To run the mpi_test.py script, which prints messages from each process:

mpiexec -n 4 python3 mpi_test.py

Expected Output

Hello from process 0
Hello from process 1
Hello from process 2
Hello from process 3

Running core_count.py

To check the number of logical cores available on your system:

python3 core_count.py

Expected output:

Logical cores: 10