Parallelization of computational tools for the no core shell model
Typ
Examensarbete för masterexamen
Program
Publicerad
2022
Författare
Hansson, Johannes
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The many-body Schrödinger equation is of fundamental importance in nuclear physics. It can
be (approximately) solved by employing the no core shell model (NCSM). Using this numerical
method in nuclear simulations is a computationally heavy task that requires powerful computer
hardware and purpose-built software. In this project we use the NCSM code JupiterNCSM to
study an eight-nucleon system, 8Be. This research code has previously only been used for nuclei
with A 6 nucleons, and our extension to study an eight-nucleon system represents a significant
increase in computational requirements. Therefore, code performance is a key factor. We find
that a single computer node running JupiterNCSM has insufficient computational power to
simulate 8Be at large model spaces. To overcome this limitation we introduce distributed-memory
parallelization to JupiterNCSM using the Message Passing Interface, which makes it possible to
use the computational capabilities of several computer nodes at the same time. In addition, we
optimize other areas of the code, such as data access patterns, to further increase performance.
As a result we have managed to extend the predictive reach of the JupiterNCSM software,
enabling the study of atomic nuclei in larger model spaces. With the memory architecture and
code optimization improvements in place, we then use JupiterNCSM to sample the posterior
predictive distribution (PPD) of the decay energy threshold of 8Be. We find that our NCSM
computations are not fully converged, which leads to low-precision predictions manifested by a
wide PPD. Still, the predictions are accurate since they reproduce the experimentally measured
decay energy. Future efforts to reach even larger model spaces and achieve better convergence
are suggested by identifying the most relevant areas for further improvement.
Beskrivning
Ämne/nyckelord
nuclear physics , no core shell model , Lanczos algorithm , large-scale matrix diagonalization , parallelization , high performance computing , MPI