Terry's alternate reservoir computing implementation

alt_echo.py

class AltEcho(Network, Reservoir):

    n_neurons = IntParam('n_neurons', default=None, low=1)
    dimensions = IntParam('dimensions', default=None, low=1)
    dt = NumberParam('dt', low=0, low_open=True)
    recurrent_synapse = SynapseParam('recurrent_synapse')
    gain = NumberParam('gain', low=0, low_open=True)
    neuron_type = NeuronTypeParam('neuron_type')

    def __init__(self, n_neurons, dimensions, recurrent_synapse=0.005,
                 readout_synapse=None, radii=1.0, gain=1.25, rng=None,
                 neuron_type=Tanh(), ens_seed=None,
                 label=None, seed=None, add_to_container=None, **ens_kwargs):

        Network.__init__(self, label, seed, add_to_container)

        self.n_neurons = n_neurons
        self.dimensions = dimensions
        self.recurrent_synapse = recurrent_synapse
        self.radii = radii  # TODO: make array or scalar parameter?
        self.gain = gain
        self.rng = np.random if rng is None else rng
        self.neuron_type = neuron_type

        self.W_in = (
            self.rng.rand(self.n_neurons, self.dimensions) - 0.5) / self.radii
        self.W_bias = self.rng.rand(self.n_neurons, 1) - 0.5
        # got the following two lines from Terry
        self.W = rng.uniform(-0.5, 0.5, size=(n_neurons, n_neurons))
        self.W *= 1.0 / np.max(np.abs(np.linalg.eigvals(self.W)**2))

        with self:
            self.ensemble = nengo.Ensemble(
                self.n_neurons, 1, neuron_type=self.neuron_type, seed=ens_seed,
                **ens_kwargs)
            self.input = nengo.Node(size_in=self.dimensions)

            pool = self.ensemble.neurons
            nengo.Connection(
                self.input, pool, transform=self.W_in, synapse=None)
            nengo.Connection(  # note the bias will be active during training
                nengo.Node(output=1, label="bias"), pool,
                transform=self.W_bias, synapse=None)
            nengo.Connection(
                self.ensemble.neurons, pool, transform=self.W,
                synapse=self.recurrent_synapse)

        Reservoir.__init__(
           self, self.input, pool, readout_synapse=readout_synapse,
           network=self)