PyTorch Learning

torches.py

import torch
import torch.nn as nn
import numpy as np
from sklearn import datasets
import matplotlib.pyplot as plt
from torch.distributions.normal import Normal
from torch.distributions.uniform import Uniform
from pprint import pprint
# 0) Prepare data
X_numpy, y_numpy = datasets.make_regression(n_samples=100, n_features=1, noise=20, random_state=4)

# cast to float Tensor
X = torch.from_numpy(X_numpy.astype(np.float32))
y = torch.from_numpy(y_numpy.astype(np.float32))
y = y.view(y.shape[0], 1)

n_samples, n_features = X.shape

# 1) Model
# Linear model f = wx + b
input_size = n_features
output_size = n_features
model = nn.Linear(input_size, output_size)

# 2) Loss and optimizer
learning_rate = 0.01

criterion = nn.MSELoss()
print(list(model.parameters()))
optimizer = torch.optim.SGD(model.parameters(), lr=learning_rate)  

# 3) Training loop
num_epochs = 100
for epoch in range(num_epochs):
    # Forward pass and loss
    y_predicted = model(X)
    loss = criterion(y_predicted, y)
    
    # Backward pass and update
    loss.backward()
    optimizer.step()

    # zero grad before new step
    optimizer.zero_grad()

    if (epoch+1) % 10 == 0:
        print(f'epoch: {epoch+1}, loss = {loss.item():.4f}')

# Plot
predicted = model(X).detach().numpy().flatten()
bias = model.bias.detach().numpy()
weight = model.weight.detach().numpy()
se = y_numpy-predicted
#pprint(list(zip(y_numpy, predicted, se)))
sigma = np.std(y_numpy-predicted, ddof=1)
mu_vec = (weight*X_numpy).flatten()
n_samples = 250

def norm_dist_sample(mu):
  rnorm_sampler = Normal(loc = mu, scale = sigma)
  rnorm = rnorm_sampler.sample((n_samples,))
  #print(f"\nmu: {mu}\nsigma: {sigma}")
  return rnorm

X_explode = torch.tensor(X_numpy).tile((n_samples,)).flatten()
dist = torch.cat(list(map(norm_dist_sample, mu_vec)))
X_ex_np = X_explode.numpy()
dist_np = dist.numpy()
plt.plot(X_numpy, predicted, '#B68D40')
plt.scatter(X_ex_np, dist_np, fc='none', ec='#122620',marker='o')
plt.scatter(X_numpy, y_numpy, fc='#F4EBD0', ec = '#F4EBD0',marker='x')
plt.show()