NengoDL 2.0.0 released

The NengoDL team is delighted to announce the release of NengoDL 2.0.0.

What is NengoDL?

NengoDL is a backend for Nengo that integrates deep learning methods (supported by the TensorFlow framework) with other Nengo modelling tools. This allows users to optimize their models using deep learning training methods, improves simulation speed (on CPU or GPU), and makes it easy to insert TensorFlow models (such as a convolutional neural network) into Nengo networks.

How do I use it?

To use NengoDL, replace instances of nengo.Simulator with nengo_dl.Simulator.

For example, if you have a network called net and you run it as

with nengo.Simulator(net) as sim:

you would change that to

with nengo_dl.Simulator(net) as sim:

and that’s it!

Information on accessing the more advanced features of NengoDL can be found in the documentation.

What’s new?

The 2.0.0 release has a lot of new content. Most significant, there are three breaking API changes:

  • sim.train and sim.loss now accept a single data argument, which combines the previous inputs and targets arguments. For example,

    sim.train({my_node: x}, {my_probe: y}, ...)

    is now equivalent to

    sim.train({my_node: x, my_probe: y}, ...)

    The motivation for this change is that not all objective functions require target values. Switching to the more generic data argument simplifies the API and makes it more flexible, allowing users to specify whatever training/loss data is actually required.

  • The objective argument in sim.train/sim.loss is now always specified as a dictionary mapping probes to objective functions. Note that this was available but optional previously; it was also possible to pass a single value for the objective function, which would be applied to all probes in targets. The latter is no longer supported. For example,

    sim.train(..., objective="mse")

    must now be explicitly specified as

    sim.train(..., objective={my_probe: "mse"})

    The motivation for this change is that, especially with the other new features introduced in the 2.0 update, there were a lot of different ways to specify the objective argument. This made it somewhat unclear how exactly this argument worked, and the automatic “broadcasting” was also ambiguous (e.g., should the single objective be applied to each probe individually, or to all of them together?). Making the argument explicit helps clarify the mental model.

  • NengoDL no longer supports Python 2. Most major Python packages will be dropping Python 2 support within a year or so, so the NengoDL 2.0 release was a good opportunity to do the same. See for more detail.

We’ve also added the sim.run_batch function, which exposes all the functionality used to implement the higher level functions. This provides a lot of flexibility for anyone looking to customize the way a NengoDL model is simulated. In the same vein, we’ve improved the flexibility of the objective argument in sim.train/loss, to make it easier to build different types of objective functions. And we’ve reorganized the documentation to make it easier to find the information you’re looking for. Check out the GitHub release page for a full changelog.

How do I get it?

To install NengoDL, we recommend using pip:

pip install nengo-dl

More detailed installation instructions can be found here.

Where can I learn more?

Where can I get help?

Please come to the Nengo forum! We welcome any questions and suggestions you might have.