Conference : Astronum 2019, Paris, France.
Title: Boosting I/O and visualization for exascale era using Hercule: test case on RAMSES.

It has been clearly identified that I/O is one of the bottleneck to extend application for the exascale
era. New concepts such as 'in transit' and 'in situ' visualization and analysis have been identified as
key technologies to circumvent this particular issue. A new parallel I/O and data management
library called HERCULE, developed at CEA-DAM (Military Applications Division), has been
integrated to RAMSES, an AMR simulation code for self-gravitating fluids. Splitting the original
RAMSES output format in HERCULE database formats dedicated to either checkpoints/restarts
(HProt format) or post-processing (HDep format) not only improved I/O performance and
scalability of the RAMSES code but also introduced much more flexibility in the simulation outputs
to help astrophysicists prepare their DMP (Data Management Plan). Furthermore, the very
lightweight and purpose-specific post-processing format (HDep) will significantly improve the
overall performance of analysis and visualization tools such as PyMSES5. An introduction to the
HERCULE parallel I/O library as well as I/O benchmark results will be presented.