# AERes

## Overview
AERes is a Python package for experimenting with the attention-enhanced reservoir architecture using PyTorch. This library includes modules to simulate dynamical systems like the Lorenz attractor, implement reservoir computing models, and apply linear attention mechanisms.
The corresponding paper can be found here:(https://arxiv.org/abs/2312.16503)

## Installation
You can install AERes using pip:

```bash
pip install aeres
```

## Quick Start

This guide will help you get started with the `AERes` library, demonstrating how to simulate a dynamical system, utilize reservoir computing, and apply both Ridge Regression and a linear attention model for analysis.

### Simulating a Dynamical System

Simulate the standard Lorenz system, a well-known example of a chaotic dynamical system, to generate synthetic time-series data.

```python
from AERes.dynamicalSystems import LorenzSimulator

# Initialize the Lorenz simulator with the 'lorenz_coupled' configuration
lorenz_simulator = LorenzSimulator(function_name='lorenz')

# Perform the simulation and retrieve the data split into training and testing sets
X_train, Y_train, X_test, Y_test = lorenz_simulator.simulate_lorenz()
```

Here, `LorenzSimulator` is used to create a Lorenz system simulation with a specified system configuration, generating training and testing datasets.

### Simulating a Reservoir

Process the simulated data through a reservoir computing system.

```python
from AERes.reservoir import Reservoir

# Create an instance of the Reservoir with specified parameters
reservoir = Reservoir(X_train, number_nodes=50, input_dimension=X_train.shape[1], seed=1, standardize=True)
```

`Reservoir` processes the input data through a fixed, random recurrent structure of tanh functions. 
The parameters such as `number_nodes`, `input_dimension`, and `standardize` control the complexity, dimensions, and state normalization, respectively.

### Training a Ridge Regression Model

Use a simple linear model, Ridge Regression, to establish a baseline for comparison with more complex models.

```python
from sklearn.linear_model import Ridge

# Train a Ridge Regression model on the processed and standardized states
ridge_model = Ridge(alpha=1.0)
ridge_model.fit(reservoir.states_stand, Y_train)

# Make predictions on the training data
ridge_predictions = ridge_model.predict(reservoir.states_stand)
```

The Ridge Regression model helps in understanding the basic performance on the dataset, using `alpha` for regularization strength.

### Implementing the Linear Attention Model

Implement a linear attention model that dynamically focuses on the most important features of the input data.

```python
from AERes.attention import LinearAttentionTrainer

# Initialize the trainer for the Linear Attention model with the standardized reservoir states
trainer = LinearAttentionTrainer(reservoir.states_stand, Y_train, layer_type="linear")

# Train the model over 100 epochs
trainer.train(epochs=100)
```

`LinearAttentionTrainer` sets up the model training process, handling both the training iterations and the data loading.

### Evaluating the Model

Compare the performance of the Ridge Regression and Linear Attention models to understand their effectiveness.

```python
# Calculate the Mean Squared Error (MSE) for the Ridge Regression model
ridge_loss = trainer.MSELoss(ridge_predictions, Y_train)
print(f'Ridge Regression MSE for training: {ridge_loss.item()}')

# Evaluate the trained attention model on the testing data
trainer.evaluate(reservoir.states_stand, Y_test)
```

The evaluation phase involves calculating the Mean Squared Error (MSE) for both models to quantify their accuracy.

We can also make predictions on some given input and plot its outcome.

```python
import matplotlib.pyplot as plt
#Get the next step prediction for the testing set and plot it
pred_test = trainer.predict(reservoir.states_stand)
plt.plot(Y_test[:,0])
plt.plot(pred_test[:,0])
plt.show()
```

To perform a closed-loop configuration, we can use the one_step function of the reservoir system.

```python
#First run a few steps to converge the reservoir on the trajectory
N = 250
for i in range(N):
    reservoir.one_step(X_test[i], standardize=True)

#Then start the system and let it run autonomously
input = X_test[N]
prediction = []
for i in range(N):
    reservoir.one_step(input, standardize=True)
    #We have to reshape the reservoir state to the right tensor dimensions. Afterwards, we have to transpose and squeeze it
    pred_test = trainer.predict(reservoir.state_stand.reshape(1, -1)).T.squeeze() 
    prediction.append(pred_test)
    input = pred_test

plt.plot(np.array(prediction)[:,0])
plt.plot(Y_test[N:,0])
plt.show()
```

### Save the Model

To save time and computation, we can save the parameters of our model and load them for later use.

```python
#We can save and load the trained model under a specified path
trainer.save_model('path_to_model.pt')
trainer.load_model('path_to_model.pt')
```

## Higher Complexity yields more performance improvement

The above example showcases the usage of the library. The classic Lorenz system is a very easy task, therefore the performance difference between the classic ridge regression approach and the linear attention is not very big. Using systems with higher complexity or more diverse time series data will enable the advantages of the linear attention approach. With time I will more examples here to show that.