Simple Digital Circuit Simulator

This example application demonstrates how a simple yet functional gate-level logic circuit simulation SpiNNaker application can be built using Rig.

In this application, each individual gate is modelled by an application core in SpiNNaker. Connections between the gates are modelled by transmitting multicast packets. Each core simply recomputes and transmits its value every millisecond based on the most recently received input values. Some applications may also be used to playback predefined stimulus signals or record the state of signals as the simulation progresses. A simple Rig-based program (circuit_sim) runs on the host taking care of mapping a description of a circuit into applications and routes, loading and configuring the machine and retrieving results.

Though this example is very simple (and makes incredibly wasteful use of SpiNNaker’s resources), its operation is analogous to the more complex task of building neural simulation software for SpiNNaker. Just as in many neural modelling applications we translate a high-level description of a problem into a graph of application cores connected by routes, map this onto a SpiNNaker machine and handle basic configuration and result retrieval.

Source code on GitHub

Usage

You’ll need to install some Python dependencies before you start:

$ pip install rig numpy matplotlib bitarray

Then make sure your board has been booted, e.g.:

$ rig-boot spinnaker-board-hostname --spin5

Two example circuits are provided which can be executed using one of:

$ python example_xor.py spinnaker-board-hostname
$ python example_flipflop.py spinnaker-board-hostname

These scripts describe (at a high level) a circuit and then run a simulation on an attached SpiNNaker board and then plot the results using matplotlib. The example_xor.py script describes an XOR gate implemented using sum-of-products and produces a plot which looks like the following where the top two waveforms are the inputs to the XOR and the bottom waveform is the output.

The circuit_sim.py file contains the full Rig-based program which maps the high level circuit description onto a SpiNNaker board and runs the model. This module has a set of complementary tests which demonstrate how to test host-side applications without the need for a SpiNNaker board to be present. The test suite’s dependencies can be installed and the tests executed using:

$ pip install pytest mock
$ py.test test_circuit_sim.py

The spinnaker_applications directory contains the C sources and compiled binaries for the SpiNNaker applications which implement the SpiNNaker-side of the simulation. See the subsection below for details of how to recompile these applications.

SpiNNaker Binary Compilation

Precompiled binaries are included in the repository so you don’t need to compile the binaries in order to play with the program as it stands. If you want to compile the SpiNNaker binaries, after sourcing the setup script in the official spinnaker low-level software release, execute the following quick-hack snippet:

cd spinnaker_applications
for f in *.c; do
    make APP=${f%.c} clean; make APP=${f%.c};
done