Improve investigating gravitational-wave sources with the help of MPI and OpenMP interface

The most recent catalog of gravitational waves compiled by the LIGO-Virgo-KAGRA collaboration contains over 90 compact-binary coalescences, mostly binary black holes. The astrophysical interpretations of the detected sources are still uncertain, although the number is expected to rise significantly over the next few years. From a theoretical point of view, one of the possible explanations for the formation of merging compact binaries is the isolated binary scenario. In this instance, two stars are gravitationally bound from the moment they are formed. During stellar evolution, stars move closer to one another, and at the end of their lives, they turn into compact remnants. As a result, a formed compact binary system has the potential to merge during the lifetime of the Universe. Binary population-synthesis codes are tools that can evolve massive populations of single or binary stars from the formation moment to the compact remnants stage. They play an essential role in the investigation of this scenario. The evolution of one binary system does not require significant computational resources. However, to obtain sufficient statistics on compact object mergers, we require simulations of billions of binary systems with different initial conditions, stellar masses, evolutionary prescriptions, and metallicities. In this project, I will implement a novel parallelization method for the SEVN code, a state-of-the-art population-synthesis code developed in SISSA and at the University of Padova. The final goal is to make the SEVN code run effectively on multi-node supercomputers. To accomplish that, I will use the Message Passing Interface (MPI) for inter-node parallelization and the Open Multi-Processing (OpenMP) interface for intra-node parallelization. Furthermore, I will also implement an automatic and adaptive data loading algorithm to load input binaries in chunks. Finally, I will investigate the weak and strong scaling of the code on various computing machines. The new code is expected to significantly speed up the evolution of binary systems, giving us the chance to investigate the formation of gravitational-wave sources in different stellar environments, possibly up to the regime of galaxies (i.e., billions of binaries).