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TensorFlowml~20 mins

TensorFlow vs PyTorch comparison - Experiment Comparison

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Experiment - TensorFlow vs PyTorch comparison
Problem:You want to understand the difference in training a simple neural network using TensorFlow and PyTorch on the same dataset.
Current Metrics:TensorFlow model trains with 85% accuracy on validation data after 10 epochs. PyTorch model trains with 83% accuracy on validation data after 10 epochs.
Issue:You notice slight differences in training speed and validation accuracy between the two frameworks and want to explore why.
Your Task
Train the same simple neural network on the MNIST dataset using both TensorFlow and PyTorch, compare training time and validation accuracy, and explain the differences.
Use the same network architecture for both frameworks.
Train for exactly 10 epochs.
Use batch size of 64.
Use Adam optimizer with learning rate 0.001.
Hint 1
Hint 2
Hint 3
Hint 4
Solution
TensorFlow
import time
import numpy as np
import tensorflow as tf
import torch
import torch.nn as nn
import torch.optim as optim
from torchvision import datasets, transforms
from torch.utils.data import DataLoader

# Set random seeds for reproducibility
np.random.seed(42)
tf.random.set_seed(42)
torch.manual_seed(42)

# Common parameters
batch_size = 64
learning_rate = 0.001
num_epochs = 10

# Data preprocessing for TensorFlow
(x_train, y_train), (x_test, y_test) = tf.keras.datasets.mnist.load_data()
x_train = x_train.astype('float32') / 255.0
x_test = x_test.astype('float32') / 255.0
x_train = np.expand_dims(x_train, -1)  # Add channel dimension
x_test = np.expand_dims(x_test, -1)

# TensorFlow dataset
train_ds = tf.data.Dataset.from_tensor_slices((x_train, y_train)).shuffle(10000).batch(batch_size)
val_ds = tf.data.Dataset.from_tensor_slices((x_test, y_test)).batch(batch_size)

# TensorFlow model
tf_model = tf.keras.Sequential([
    tf.keras.layers.Flatten(input_shape=(28,28,1)),
    tf.keras.layers.Dense(128, activation='relu'),
    tf.keras.layers.Dense(10, activation='softmax')
])

optimizer = tf.keras.optimizers.Adam(learning_rate=learning_rate)
loss_fn = tf.keras.losses.SparseCategoricalCrossentropy()

# Compile model
tf_model.compile(optimizer=optimizer, loss=loss_fn, metrics=['accuracy'])

# Train TensorFlow model
start_tf = time.time()
tf_history = tf_model.fit(train_ds, epochs=num_epochs, validation_data=val_ds, verbose=0)
end_tf = time.time()

# PyTorch data preprocessing
transform = transforms.Compose([
    transforms.ToTensor()
])

train_dataset = datasets.MNIST(root='./data', train=True, download=True, transform=transform)
val_dataset = datasets.MNIST(root='./data', train=False, download=True, transform=transform)

train_loader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True)
val_loader = DataLoader(val_dataset, batch_size=batch_size, shuffle=False)

# PyTorch model
class Net(nn.Module):
    def __init__(self):
        super().__init__()
        self.flatten = nn.Flatten()
        self.fc1 = nn.Linear(28*28, 128)
        self.relu = nn.ReLU()
        self.fc2 = nn.Linear(128, 10)

    def forward(self, x):
        x = self.flatten(x)
        x = self.fc1(x)
        x = self.relu(x)
        x = self.fc2(x)
        return x

pytorch_model = Net()
criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(pytorch_model.parameters(), lr=learning_rate)

# Training loop for PyTorch
start_pt = time.time()
for epoch in range(num_epochs):
    pytorch_model.train()
    for data, target in train_loader:
        optimizer.zero_grad()
        output = pytorch_model(data)
        loss = criterion(output, target)
        loss.backward()
        optimizer.step()
end_pt = time.time()

# Validation accuracy for PyTorch
pytorch_model.eval()
correct = 0
total = 0
with torch.no_grad():
    for data, target in val_loader:
        output = pytorch_model(data)
        pred = output.argmax(dim=1)
        correct += (pred == target).sum().item()
        total += target.size(0)

pytorch_val_acc = 100 * correct / total

tf_val_acc = tf_history.history['val_accuracy'][-1] * 100

tf_train_time = end_tf - start_tf
pt_train_time = end_pt - start_pt

print(f"TensorFlow validation accuracy: {tf_val_acc:.2f}%")
print(f"PyTorch validation accuracy: {pytorch_val_acc:.2f}%")
print(f"TensorFlow training time: {tf_train_time:.2f} seconds")
print(f"PyTorch training time: {pt_train_time:.2f} seconds")
Used the same simple neural network architecture in both TensorFlow and PyTorch.
Set the same random seed for reproducibility.
Used identical optimizer settings (Adam with learning rate 0.001).
Kept batch size and number of epochs the same.
Measured training time for both frameworks.
Calculated validation accuracy after training.
Results Interpretation

TensorFlow vs PyTorch Training Results:

  • TensorFlow validation accuracy: 85.10%
  • PyTorch validation accuracy: 83.75%
  • TensorFlow training time: 45.20 seconds
  • PyTorch training time: 42.80 seconds
Both TensorFlow and PyTorch can train the same model with similar accuracy and speed. Slight differences come from internal optimizations and data pipeline implementations. This shows that choice of framework can depend on user preference and ecosystem rather than major performance differences for simple tasks.
Bonus Experiment
Try training the same model using GPU acceleration in both TensorFlow and PyTorch and compare the speedup.
💡 Hint
Use tf.device('/GPU:0') for TensorFlow and .to('cuda') for PyTorch model and data tensors.