System modeling for process mapping on toscattered computational nodes in highperformance computing clusters

Sammanfattning: The task of assigning a parallel program’s processes to processorsin a computer system is referred to as process mapping.It is desired that such a mapping results in communication being kept as local as possible in the system while also achieving load balance between computational units, as this would reduce program execution time. By representing the program and the system as graphs, the problem can be defined and solved using existing graph algorithms. In this thesis we study the process of modeling virtual systems consisting of scattered nodes in a supercomputer, in a way that process mapping can be performed with these models. Although the supercomputer has a structured interconnection network that forms a 3D torus, the subsets of the system that are modeled and used for program execution are spread out in the system and hence they themselves do not form a logical topology. We present and evaluate two methods for model creation, both based on measurements performed on the system.