Guaranteeing spike arrival time in multiboard & multichip spiking neural networks

Large-scale spiking neural networks (SNN) are generally run on distributed and parallel architectures with multiple computation nodes. These architectures induce extra delays due to the node-to-node communication process. In multiboard & multichip SNNs, important delays may affect spike arrival time and, thus, can alter simulation results. In this work, we propose a method aiming to guarantee spike arrival time with arbitrary prefixed deadlines. The communication architecture is based on the token-passing access policy to grant access to shared communication channels. We show that several network parameters must be set carefully if spikes have to meet their deadlines. Parameters are chosen by taking into account the communication channel bandwidth, the arbitrary deadlines and the worst case situation that can happen in generating neural activity in SNNs. As proof of concept, we have built a system that emulates up to 120 analog Hodgkin-Huxley neurons spread across 6 boards. Experimental results show that whatever it happens (unless there is a network fault), spikes reach their destination with a maximum delay of 5 microseconds.