Neuron Parameters remain unchanged after setting them and also after training them.

[Naveed Unjum]

When building the network, the neuron parameters that need to be set don't seem to change even after setting different values.
For example, for the following network:

self.blocks = torch.nn.ModuleList([
                slayer.block.cuba.Dense(neuron_params, 18, 20),
                slayer.block.cuba.Dense(neuron_params, 20, 18)
     ])

with

neuron_params = {
                'threshold': 1,
                'current_decay': 1,
                'voltage_decay': 1,
                'requires_grad': True,     
            }

when checked from inside the network gives:

for block in net.blocks:
    print(block)
    print("Voltage", block.neuron.voltage_decay)
    print("Current", block.neuron.current_decay)
    print("Threshold", block.neuron.threshold)

<<<<<OUTPUT>>>>>>
Dense(
  (neuron): Neuron()
  (synapse): Dense(18, 20, kernel_size=(1, 1, 1), stride=(1, 1, 1), bias=False)
)
Voltage Parameter containing:
tensor([4096.], requires_grad=True)
Current Parameter containing:
tensor([4096.], requires_grad=True)
Threshold :1

We see from the source code the decay is scaled by 1<<12, so we get 4096.
But when changing the neuron parameters to

neuron_params = {
                'threshold': 10,
                'current_decay': 10,
                'voltage_decay': 10,
                'requires_grad': True,     
            }

we only see the threshold changing inside the network

Dense(
  (neuron): Neuron()
  (synapse): Dense(18, 20, kernel_size=(1, 1, 1), stride=(1, 1, 1), bias=False)
)
Voltage Parameter containing:
tensor([4096.], requires_grad=True)
Current Parameter containing:
tensor([4096.], requires_grad=True)
Threshold 10.0

The voltage and current decay remain the same.

After training the network with SpikeTime Loss(Oxford tutorial) with requires_grad=True, we again see don't see the threshold changing, and the only the decay changes by a very small amount.

  (neuron): Neuron()
  (synapse): Dense(18, 20, kernel_size=(1, 1, 1), stride=(1, 1, 1), bias=False)
)
Voltage Parameter containing:
tensor([4095.0273], requires_grad=True)
Current Parameter containing:
tensor([4095.0273], requires_grad=True)
Threshold 1.0
********************
Dense(
  (neuron): Neuron()
  (synapse): Dense(20, 18, kernel_size=(1, 1, 1), stride=(1, 1, 1), bias=False)
)
Voltage Parameter containing:
tensor([4096.0005], requires_grad=True)
Current Parameter containing:
tensor([4096.0005], requires_grad=True)
Threshold 1.0

Steps to reproduce the behavior:

1. In the oxford tutorial, set the neuron_params and print the neuron parameters using this:

for block in net.blocks:
    print(block)
    print("Voltage", block.neuron.voltage_decay)
    print("Current", block.neuron.current_decay)
    print("Threshold", block.neuron.threshold)
    print("********************")

2. Try changing the neuron parameters, there is no effect on the decay parameters,
3. Train the model, only decay parameters by a small margin, while threshold remains the same.

I don't know if the issue is with the implementation or my Code. Can someone cross check this?

[bamsumit]

1. current_decay and voltage_decay need to be between 0 and 1. So a value of 10 is most likely getting clamped in this valid range.
2. Thresholds in CUBA-LIF neurons are not learnable.