Impact of exponential long range and Gaussian short range lateral connectivity on the distributed simulation of neural networks including up to 30 billion synapses

Recent experimental neuroscience studies are pointing out the role of long-range intra-areal connectivity that can be modeled by a distance dependent exponential decay of the synaptic probability distribution. This short report provides a preliminary measure of the impact of exponentially decaying lateral connectivity compared to that of shorter-range Gaussian decays on the scaling behaviour and memory occupation of a distributed spiking neural network simulator (DPSNN). Two-dimensional grids of cortical columns composed by point-like spiking neurons have been connected by up to 30 billion synapses using exponential and Gaussian connectivity models. Up to 1024 hardware cores, hosted on a 64 nodes server platform, executed the MPI processes composing the distributed simulator. The hardware platform was a cluster of IBM NX360 M5 16-core compute nodes, each one containing two Intel Xeon Haswell 8-core E5-2630 v3 processors, with a clock of 2.40GHz, interconnected through an InfiniBand network. This study is conducted in the framework of the CORTICONIC FET project, also in view of the next -to-start activities foreseen as part of the Human Brain Project (HBP), SubProject 3 Cognitive and Systems Neuroscience, WaveScalES work-package.