September 2, 2024

Gradient Echo: Pioneering the Future of Deep Learning

Photo by Maxim Berg on Unsplash

Copy and paste the text into a new notebook in Google Colab, then run the code.

!pip install torch norse

import gym
import torch
import torch.nn as nn
import torch.optim as optim
import numpy as np
import norse.torch as norse

# Gradient Echo Layer
class GradientEchoLayer(nn.Module):
    def __init__(self, input_size, output_size, echo_factor=0.9, memory_size=5):
        super(GradientEchoLayer, self).__init__()
        self.fc = nn.Linear(input_size, output_size)
        self.echo_factor = echo_factor
        self.memory_size = memory_size
        self.gradient_memory = []

    def forward(self, x):
        return torch.relu(self.fc(x))

    def modify_grad(self, grad):
        if len(self.gradient_memory) > 0 and grad.shape != self.gradient_memory[0].shape:
            self.gradient_memory = []

        if len(self.gradient_memory) >= self.memory_size:
            self.gradient_memory.pop(0)
        self.gradient_memory.append(grad.clone().detach())

        echo_grad = torch.zeros_like(grad)
        for i, past_grad in enumerate(reversed(self.gradient_memory)):
            echo_grad += self.echo_factor ** i * past_grad

        return grad + echo_grad

    def register_hooks(self):
        self.fc.weight.register_hook(self.modify_grad)
        self.fc.bias.register_hook(self.modify_grad)

# Policy Network with Gradient Echo
class PolicyNetwork(nn.Module):
    def __init__(self, input_size, hidden_size, output_size):
        super(PolicyNetwork, self).__init__()
        self.layer1 = GradientEchoLayer(input_size, hidden_size)
        self.fc2 = nn.Linear(hidden_size, hidden_size)
        self.fc3 = nn.Linear(hidden_size, output_size)

        self.layer1.register_hooks()

    def forward(self, x):
        x = self.layer1(x)
        x = torch.relu(self.fc2(x))
        return torch.softmax(self.fc3(x), dim=-1)

# Liquid State Machine (LSM) for reward processing
class LiquidStateLayer(nn.Module):
    def __init__(self, input_size, hidden_size):
        super(LiquidStateLayer, self).__init__()
        self.lif = norse.LIFCell()  # Leaky Integrate-and-Fire neuron model
        self.fc = nn.Linear(input_size, hidden_size)
    
    def forward(self, x, state=None):
        x = self.fc(x)
        out, state = self.lif(x, state)
        return out, state

# Surrogate Model with LSM and Gradient Echo for reward prediction
class SurrogateModelWithLSM(nn.Module):
    def __init__(self, input_size, liquid_hidden_size, hidden_size):
        super(SurrogateModelWithLSM, self).__init__()
        self.liquid_state_layer = LiquidStateLayer(input_size, liquid_hidden_size)
        self.gradient_echo_layer = GradientEchoLayer(liquid_hidden_size, hidden_size)
        self.fc2 = nn.Linear(hidden_size, 1)

        self.gradient_echo_layer.register_hooks()

    def forward(self, x, symbolic_output):
        state = None  # Initialize state for LIF neurons
        liquid_out, state = self.liquid_state_layer(x, state)
        x = torch.relu(self.gradient_echo_layer(liquid_out))
        
        # Reward adjustment based on symbolic reasoning
        reward = self.fc2(x)
        if symbolic_output['risk'] == "freeze":
            reward -= 1
        elif symbolic_output['risk'] == "dry_out":
            reward -= 0.5
            
        return reward

# Simple Neural Network for symbolic reasoning
class SimpleNN(nn.Module):
    def __init__(self):
        super(SimpleNN, self).__init__()
        self.fc1 = nn.Linear(10, 64)
        self.fc2 = nn.Linear(64, 32)
        self.fc3 = nn.Linear(32, 2)

    def forward(self, x):
        x = torch.relu(self.fc1(x))
        x = torch.relu(self.fc2(x))
        return torch.sigmoid(self.fc3(x))  # Output between 0 and 1 for binary decision

# Symbolic reasoning based on environmental factors
def symbolic_reasoning(rain, sprinkler, temperature):
    wet = rain or sprinkler
    if temperature < 0:
        risk = "freeze"
    elif temperature > 30:
        risk = "dry_out"
    else:
        risk = "normal"
    return {"wet": wet, "risk": risk}

# Decision making based on neural and symbolic outputs
def hybrid_decision_making(nn_output, symbolic_output):
    nn_output = nn_output.squeeze()
    if symbolic_output['risk'] == "freeze" and nn_output[0] > nn_output[1]:
        return "Action A"
    elif symbolic_output['risk'] == "dry_out" and nn_output[1] > nn_output[0]:
        return "Action B"
    return "Action B" if symbolic_output['wet'] else "Action A"

# Action selection function
def select_action(state, symbolic_output, surrogate_model):
    state_tensor = torch.tensor(state, dtype=torch.float32)
    action_probs = policy_net(state_tensor)
    action = torch.multinomial(action_probs, 1).item()
    log_prob = torch.log(action_probs[action])
    symbolic_decision = hybrid_decision_making(action_probs, symbolic_output)
    predicted_reward = surrogate_model(state_tensor, symbolic_output)
    
    return action, log_prob, symbolic_decision, predicted_reward

# Meta-learning update function
def meta_learning_update(policy_net, optimizer, rewards, log_probs, surrogate_model, surrogate_optimizer, states, symbolic_outputs, discount_factor=0.99):
    discounted_rewards = []
    for t in range(len(rewards)):
        Gt = sum([r * (discount_factor ** i) for i, r in enumerate(rewards[t:])])
        discounted_rewards.append(Gt)
    discounted_rewards = torch.tensor(discounted_rewards)
    discounted_rewards = (discounted_rewards - discounted_rewards.mean()) / (discounted_rewards.std() + 1e-9)  # Normalize rewards

    loss = -sum([log_prob * Gt for log_prob, Gt in zip(log_probs, discounted_rewards)])

    optimizer.zero_grad()
    loss.backward()
    torch.nn.utils.clip_grad_norm_(policy_net.parameters(), 1.0)  # Gradient clipping
    optimizer.step()

    # Update the surrogate model using the true rewards and states
    surrogate_optimizer.zero_grad()
    surrogate_loss = 0
    for state, symbolic_output, Gt in zip(states, symbolic_outputs, discounted_rewards):
        surrogate_loss += ((surrogate_model(state, symbolic_output) - Gt) ** 2).mean()
    surrogate_loss.backward()
    surrogate_optimizer.step()

# Set up the environment using the new step API
env = gym.make('CartPole-v1', new_step_api=True)

# Initialize Policy Network and Surrogate Model with LSM for reward prediction
policy_net = PolicyNetwork(input_size=env.observation_space.shape[0],
                           hidden_size=128,
                           output_size=env.action_space.n)

surrogate_model = SurrogateModelWithLSM(input_size=env.observation_space.shape[0],
                                        liquid_hidden_size=128,
                                        hidden_size=128)

# Initialize the Simple Neural Network for symbolic reasoning
simple_nn = SimpleNN()

optimizer = optim.Adam(policy_net.parameters(), lr=0.001)
surrogate_optimizer = optim.Adam(surrogate_model.parameters(), lr=0.001)

# Run the training loop
num_episodes = 3000
for episode in range(num_episodes):
    state = env.reset()
    done = False
    rewards = []
    log_probs = []
    states = []
    symbolic_outputs = []

    while not done:
        # Generate random input for the symbolic NN
        symbolic_input = torch.randn(1, 10)
        symbolic_nn_output = simple_nn(symbolic_input)
        temperature = np.random.uniform(-5, 40)  # Random temperature input
        symbolic_output = symbolic_reasoning(rain=True, sprinkler=False, temperature=temperature)

        action, log_prob, symbolic_decision, predicted_reward = select_action(state, symbolic_output, surrogate_model)
        state, reward, done, truncated, _ = env.step(action)
        rewards.append(reward)
        log_probs.append(log_prob)
        states.append(torch.tensor(state, dtype=torch.float32))
        symbolic_outputs.append(symbolic_output)

        if done or truncated:
            meta_learning_update(policy_net, optimizer, rewards, log_probs, surrogate_model, surrogate_optimizer, torch.stack(states), symbolic_outputs)
            total_reward = sum(rewards)
            if episode % 100 == 0:
                print(f"Episode {episode}, Total Reward: {total_reward}, Symbolic Decision: {symbolic_decision}")
            break

env.close()


      
# Copyright 2024 square play

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# you may not use this file except in compliance with the License.
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