Understanding SGD Optimizer and Learning Rate in PyTorch

What will you learn?

In this tutorial, you will learn how to implement Stochastic Gradient Descent (SGD) with a specific learning rate, iterating over batches and epochs in PyTorch. By understanding the optimization process in deep learning, you will gain insights into enhancing model performance.

Introduction to Problem and Solution

When training neural networks, optimizing model parameters is crucial for improving accuracy. The Stochastic Gradient Descent (SGD) optimizer offers a simple yet effective solution for adjusting these parameters, especially when working with large datasets or online training scenarios.

To address this challenge, we will set up our environment using PyTorch, structure our dataset into batches, define the neural network architecture, and configure the SGD optimizer with a custom learning rate (lr). By iterating through the dataset over multiple epochs and updating model weights using backpropagation during each batch iteration, we will witness the iterative refinement of our model.


import torch
import torch.nn as nn
import torch.optim as optim

# Define your model structure here
class YourModel(nn.Module):
    def __init__(self):
        super(YourModel, self).__init__()
        # Define layers here

    def forward(self, x):
        # Implementation of forward pass 
        return x

model = YourModel()
criterion = nn.CrossEntropyLoss()
optimizer = optim.SGD(model.parameters(), lr=0.01)

# Assuming 'data_loader' is your DataLoader instance containing batched data
for epoch in range(num_epochs):  
    for inputs, labels in data_loader:

        outputs = model(inputs)
        loss = criterion(outputs, labels)



    print(f"Epoch {epoch+1}, Loss: {loss.item()}")

# Copyright PHD


  • Defining Our Model: Create a neural network class inheriting from nn.Module to define its structure and forward pass logic.
  • Setting Up Loss Function & Optimizer: Use CrossEntropyLoss for computing loss and SGD optimizer with a specified learning rate (lr=0.01).
  • Training Over Batches & Epochs: Iterate through batches within epochs to update model weights based on computed gradients using backpropagation.

This iterative process leads to gradual improvement in minimizing loss and enhancing model performance.

  1. What is Stochastic Gradient Descent?

  2. Stochastic Gradient Descent (SGD) is an iterative optimization method that approximates gradients using randomly sampled data points instead of the entire dataset.

  3. Why Use SGD Over Other Optimizers?

  4. SGD’s simplicity and effectiveness make it a popular choice for optimizing models quickly and efficiently, particularly in scenarios involving large datasets or real-time updates.

  5. How Does Batch Size Affect Training?

  6. Batch size influences computational efficiency and memory usage during training by determining the number of samples processed before updating model parameters.

  7. What’s The Role Of Learning Rate?

  8. The learning rate controls the step size taken during optimization; finding an optimal value is crucial for convergence without overshooting or slow progress.

  9. Can We Change LR During Training?

  10. Yes! Adaptive strategies like changing learning rates dynamically can improve convergence speed and overall optimization outcomes based on training progress feedback.


Mastering SGD optimization techniques in PyTorch involves understanding key concepts behind neural network training processes. By grasping essential principles such as selecting appropriate learning rates across iterations and epochs while fine-tuning models with care, you pave the way for successful deep learning endeavors. Embrace this knowledge to embark on rewarding machine learning adventures ahead!

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