Saturday, February 16, 2019
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Speaking about my experience in the development of algorithms with the use of octrees at CIMNE Barcelona

My name is Jorge López Ruiz, I am a PhD student in Computer Sciences at the Center for
Research in Mathematics ( CIMAT ) in Guanajuato, México. I am Industrial Engineer by the
Autonomous University of Aguascalientes and I have a Computer Sciences master degree
by CIMAT. Thanks to the Tri Continental Alliance in Numerical Methods applied to Natural
Disasters (TCAiNMaND) project, Dr. Abell Col Sans and Dr. Pooyan Dadvand I had the
opportunity to carry out a research stay at CIMNE Barcelona, where I developed parallel
algorithms using a octree data structure.
During my stay I learned a lot about numerical methods applied on sciences and
engineering, I had the opportunity to develop two parallel algorithms using a octree data
structure. The first algorithm is the collision detection of spheres and the second is a octree
mesher, both algorithms are parallelized using a distributed memory scheme with openMPI.
The first algorithm searches collisions between spheres contained on a domain and the main
purpose is to use the algorithm on numerical simulations using particle methods as Discrete
Element Method (DEM), while I was developing the algorithm, I worked with Carlos Roig and
learned a lot about high performance computing when programming with openMPI. The
results obtained showed that the algorithm works efficiently and compared with the serial
version the execution time is reduced considerably.
The second algorithm, the mesher, consists in the development of a tetrahedral mesher by
using a octree data structure. In this case I know more about the topic and it was easiest to
develop the algorithm, the most difficult part developed of the algorithm was the
communication procedures because the core goal is to make the less amount of
communications, and the information packages have to be the smallest possible. The
algorithm generates the interior mesh of a given boundary mesh and this is used when a
simulation is carried out. The Finite Element numerical simulations showed that the meshes
generated obtain accurate results and with the expected physical behavior.
Thanks to the GiD and Kratos teams by support me when doubts appeared during the
developments. I am grateful to all the coworkers for the pleasant way in which they made me
part of their team, we had the opportunity to work together, and also to carry out weekend
activities such as the fronton.
This stay was possible by the financial support of TCAiNMaND, European Union, CIMAT,
and by the opportunity that Dr. Salvador Botello from CIMAT gave me to work on a
international research center such as CIMNE.

The research leading to these results has received funding from the European Community's Seventh Framework Programme, Marie Curie International Research Staff Exchange Scheme (IRSES) under grant agreement n° 612607
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