Elastic execution of checkpointed MPI applications

MPI applications begin with a fixed number of rank and, by default, the rank remains constant throughout the application's lifetime. The developer can choose to increase the rank by dynamically spawning MPI processes. However doing this manually adds complexity to the MPI application. Making the MPI applications malleable \cite{b20} would allow HPC applications to have the same elasticity as that of cloud applications. We propose multiple approaches to change the rank of an MPI program agnostic to the modification of the user code. We use checkpointing as a tool to achieve mutability of rank by halting the execution and resuming the MPI program with a new state. In this paper, we focus on the scenario of increasing the rank of an MPI program using ExaMPI as the implementation for MPI.