Generative Adversarial Network for MNIST Dataset

computer_vision/Generative_Adversarial_Network_MNIST.py

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+"""
+Generative Adversarial Network
+
+Objective : To train a GAN model to generate handwritten digits that can be transferred to other domains.
+
+Resources GAN Theory :
+    https://en.wikipedia.org/wiki/Generative_adversarial_network
+Resources PyTorch: https://pytorch.org/
+
+Download dataset from :
+PyTorch internal function
+
+1. Fetch the Dataset with PyTorch function.
+2. Create Dataloader.
+3. Create Discriminator and Generator.
+4. Set the hyperparameters and models.
+5. Set the loss functions.
+6. Create the training loop.
+7. Visualize the losses.
+8. Visualize the result from GAN.
+
+"""
+
+
+
+
+%matplotlib inline
+
+import numpy as np
+import torch
+import matplotlib.pyplot as plt
+from torchvision import datasets
+import torchvision.transforms as transforms
+
+# number of subprocesses to use for data loading
+num_workers = 0
+# how many samples per batch to load
+batch_size = 64
+
+# convert data to torch.FloatTensor
+transform = transforms.ToTensor()
+
+# get the training datasets
+train_data = datasets.MNIST(root='data', train=True,
+                                   download=True, transform=transform)
+
+# prepare data loader
+train_loader = torch.utils.data.DataLoader(train_data, batch_size=batch_size,
+                                           num_workers=num_workers)
+
+import torch.nn as nn
+import torch.nn.functional as F
+
+# Creating Generator and Discriminator for GAN
+
+class discriminator(nn.Module):
+  def __init__(self,input_size,output_size,hidden_dim):
+    super(discriminator,self).__init__()
+
+    #defining the layers of the discriminator
+    self.fc1 = nn.Linear(input_size,hidden_dim*4)
+    self.fc2 = nn.Linear(hidden_dim*4,hidden_dim*2)
+    self.fc3 = nn.Linear(hidden_dim*2,hidden_dim)
+    #final fully connected layer
+    self.fc4 = nn.Linear(hidden_dim,output_size)
+    #dropout layer
+    self.dropout = nn.Dropout(0.2)
+
+  def forward(self,x):
+    # pass x through all layers
+    # apply leaky relu activation to all hidden layers
+    x = x.view(-1,28*28) #flattening the image
+    x = F.leaky_relu(self.fc1(x),0.2)
+    x = self.dropout(x)
+    x = F.leaky_relu(self.fc2(x),0.2)
+    x = self.dropout(x)
+    x = F.leaky_relu(self.fc3(x),0.2)
+    x = self.dropout(x)
+    x_out = self.fc4(x)
+
+    return x_out
+
+class generator(nn.Module):
+
+  def __init__(self, input_size, output_size,hidden_dim):
+    super(generator, self).__init__()
+
+    # define all layers
+    self.fc1 = nn.Linear(input_size,hidden_dim)
+    self.fc2 = nn.Linear(hidden_dim,hidden_dim*2)
+    self.fc3 = nn.Linear(hidden_dim*2,hidden_dim*4)
+    #final layer
+    self.fc4 = nn.Linear(hidden_dim*4,output_size)
+    #dropout layer
+    self.dropout = nn.Dropout(0.2)
+
+
+  def forward(self, x):
+    # pass x through all layers
+    # final layer should have tanh applied
+    x = F.leaky_relu(self.fc1(x),0.2)
+    x = self.dropout(x)
+    x = F.leaky_relu(self.fc2(x),0.2)
+    x = self.dropout(x)
+    x = F.leaky_relu(self.fc3(x),0.2)
+    x = self.dropout(x)
+    x_out = F.tanh(self.fc4(x))
+    return x_out
+
+# Calculate losses
+def real_loss(D_out, smooth=False):
+    # compare logits to real labels
+    # smooth labels if smooth=True
+    #puting it into cuda
+    batch_size = D_out.size(0)
+    if smooth:
+        labels = torch.ones(batch_size).cuda()*0.9
+    else:
+        labels = torch.ones(batch_size).cuda()
+    criterion = nn.BCEWithLogitsLoss()
+    loss = criterion(D_out.squeeze(),labels)
+    return loss
+
+def fake_loss(D_out):
+    # compare logits to fake labels
+    batch_size = D_out.size(0)
+    labels = torch.zeros(batch_size).cuda()
+    criterion = nn.BCEWithLogitsLoss()
+    loss = criterion(D_out.squeeze(),labels)
+    return loss
+
+# Discriminator hyperparams
+# Size of input image to discriminator (28*28)
+input_size = 784
+# Size of discriminator output (real or fake)
+d_output_size = 1
+# Size of *last* hidden layer in the discriminator
+d_hidden_size = 32
+
+# Generator hyperparams
+
+# Size of latent vector to give to generator
+z_size = 100
+# Size of discriminator output (generated image)
+g_output_size = 784
+# Size of *first* hidden layer in the generator
+g_hidden_size = 32
+
+# instantiate discriminator and generator and put it in cuda mode
+D = discriminator(input_size, d_output_size,d_hidden_size).cuda()
+G = generator(z_size, g_output_size, g_hidden_size).cuda()
+
+import pickle as pkl
+
+# training hyperparams
+num_epochs = 40
+
+# keep track of loss and generated, "fake" samples
+samples = []
+losses = []
+
+print_every = 400
+
+# Get some fixed data for sampling. These are images that are held
+# constant throughout training, and allow us to inspect the model's performance
+sample_size=16
+fixed_z = np.random.uniform(-1, 1, size=(sample_size, z_size))
+fixed_z = torch.from_numpy(fixed_z).float().cuda()
+
+# train the network
+D.train()
+G.train()
+for epoch in range(num_epochs):
+
+    for batch_i, (real_images, _) in enumerate(train_loader):
+
+        batch_size = real_images.size(0)
+
+        ## Important rescaling step ## 
+        real_images = (real_images*2 - 1).cuda()  # rescale input images from [0,1) to [-1, 1)
+
+        # ============================================
+        #            TRAIN THE DISCRIMINATOR
+        # ============================================
+        d_optimizer.zero_grad()
+        # 1. Train with real images
+
+        # Compute the discriminator losses on real images
+        # use smoothed labels
+        D_real = D(real_images)
+        d_real_loss = real_loss(D_real,smooth=True)
+        # 2. Train with fake images
+
+        # Generate fake images
+        z = np.random.uniform(-1, 1, size=(batch_size, z_size))
+        z = torch.from_numpy(z).float().cuda()
+        fake_images = G(z)
+
+        # Compute the discriminator losses on fake images        
+        D_fake = D(fake_images)
+        d_fake_loss = fake_loss(D_fake)
+        # add up real and fake losses and perform backprop
+        d_loss = d_real_loss + d_fake_loss
+        d_loss.backward()
+        d_optimizer.step()
+
+
+        # =========================================
+        #            TRAIN THE GENERATOR
+        # =========================================
+        g_optimizer.zero_grad()
+        # 1. Train with fake images and flipped labels
+
+        # Generate fake images
+        z = np.random.uniform(-1, 1, size=(batch_size, z_size))
+        z = torch.from_numpy(z).float().cuda()
+        fake_images = G(z)
+        # Compute the discriminator losses on fake images 
+        # using flipped labels!
+        D_fake = D(fake_images)
+        # perform backprop
+        g_loss = real_loss(D_fake)
+        g_loss.backward()
+        g_optimizer.step()
+
+
+        # Print some loss stats
+        if batch_i % print_every == 0:
+            # print discriminator and generator loss
+            print('Epoch [{:5d}/{:5d}] | d_loss: {:6.4f} | g_loss: {:6.4f}'.format(
+                    epoch+1, num_epochs, d_loss.item(), g_loss.item()))
+
+
+    ## AFTER EACH EPOCH##
+    # append discriminator loss and generator loss
+    losses.append((d_loss.item(), g_loss.item()))
+
+    # generate and save sample, fake images
+    G.eval() # eval mode for generating samples
+    samples_z = G(fixed_z)
+    samples.append(samples_z)
+    G.train() # back to train mode
+
+
+# Save training generator samples
+with open('train_samples.pkl', 'wb') as f:
+    pkl.dump(samples, f)
+
+#ploting Discriminator and Generator loss
+fig, ax = plt.subplots()
+losses = np.array(losses)
+plt.plot(losses.T[0], label='Discriminator')
+plt.plot(losses.T[1], label='Generator')
+plt.title("Training Losses")
+plt.legend()
+plt.show()
+
+
+#Viewing the results of the GAN
+def view_samples(epoch, samples):
+
+  fig, axes = plt.subplots(figsize=(7,7), nrows=4, ncols=4, sharey=True, sharex=True)
+  fig.suptitle("Generated Digits")
+  for ax, img in zip(axes.flatten(), samples[epoch]):
+      img = img.detach().cpu().numpy()
+      ax.xaxis.set_visible(False)
+      ax.yaxis.set_visible(False)
+      im = ax.imshow(img.reshape((28,28)), cmap='Greys_r')
+
+with open('train_samples.pkl', 'rb') as f:
+  samples = pkl.load(f)
+
+view_samples(-1,samples)
+plt.show()  
+