Relaxation Technique Parallelised in C using Pthreads and MPI

Problem Description

The objective of this assignment is to use low-level primitive parallelism constructs, first on a shared memory architecture then on a distributed memory architecture, and analyse how parallel problems scale on such an architectures using C, pthreads and MPI on Balena, a mid-sized cluster with 2720 cpu cores.

The background is a method called relaxation technique, a solution to differential equations, which is achieved by having a square array of values and repeatedly replacing a value with the average of its four neighbours, excepting boundaries values which remain fixed. This process is repeated until all values settle down to within a given precision.

Usage

Shared Memory Architecture (pthreads)

• Compile using the makefile: make, or gcc main.c array_helpers.c print_helpers.c -o shared_relaxation -pthread -Wall -Wextra -Wconversion
• Run: ./shared_relaxation <number_of_threads>

Distributed Memory Architecture (MPI)

• Compile using the makefile: make or: mpicc -Wall -Wextra -Wconversion main.c -o distributed_relaxation -lm
• Run: mpirun -np <num_processes> ./distributed_relaxation -d <dimension> -p <precision> -debug <debug mode>

where:

• -np corresponds to the number of processes;
• -d corresponds to the dimensions of the square array;
• -p corresponds to the precision of the relaxation;
• -debug corresponds to the debug mode (0: only essential information, 1: row allocation logs, 2: process IDs logs, 3: initial and nal arrays, 4: iteration debugging data).

Other

Running the shared memory architecture on the Balena cluster using SLURM

• SSH into Balena: ssh [user_name]@balena.bath.ac.uk
• cd into the project directory and submit the SLURM job script job.slurm to the queue: sbatch jobscript.slurm
• Monitor the job in the queue: squeue -u [user_name]
• View the results in the relaxation.<job_id>.out file using the cat *.out command.

Submitting multiple files using a bash script (shared memory testing)

• ./submit_multiple_batch 1
• cat *.out
• Use following regex to retrieve time by using this regex \=.(\d+)\..(\d+) and pasting the output in regex101

Copying files to/from Balena

• from BUCS to Balena: cp $BUCSHOME/dos/year\ 4/Relaxation-Technique-Parallel-Computing/src/<file> /home/o/aj645/scratch/cw2-distributed-architecture/

• from Balena to BUCS: cp /home/o/aj645/scratch/cw2-distributed-architecture/<file> $BUCSHOME/dos/year\ 4/Relaxation-Technique-Parallel-Computing

Reports

• You can read the shared architecture implementation using pthreads report here.
• You can read the distributed architecture implementation using MPI report here.

TODO

See TODO.md

License

• see LICENSE file.

Contact

• email: adam@jaamour.com
• website: www.adam.jaamour.com
• twitter: @Adamouization