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Train models with PyTorch in Microsoft Fabric

This article describes how to train and track the iterations of a PyTorch model. The PyTorch machine learning framework is based on the Torch library. PyTorch is often used for computer vision and natural language processing applications.

Prerequisites

Install PyTorch and torchvision in your notebook. Install or upgrade the libraries in your environment with:

pip install torch torchvision

Set up the machine learning experiment

Create a machine learning experiment with the MLflow API. The MLflow set_experiment() function creates the experiment named sample-pytorch if it doesn't exist.

Run the following code in your notebook to create the experiment:

import mlflow

mlflow.set_experiment("sample-pytorch")

Train and evaluate a PyTorch model

After you set up the experiment, load the Modified National Institute of Standards and Technology (MNIST) dataset. Generate the training and test datasets, then create a training function.

Run this code in your notebook to train the PyTorch model:

import os
import torch
import torch.nn as nn
from torch.autograd import Variable
import torchvision.datasets as dset
import torchvision.transforms as transforms
import torch.nn.functional as F
import torch.optim as optim

# Load the MNIST dataset
root = "/tmp/mnist"
if not os.path.exists(root):
    os.mkdir(root)

trans = transforms.Compose(
    [transforms.ToTensor(), transforms.Normalize((0.5,), (1.0,))]
)

# If the data doesn't exist, download the MNIST dataset
train_set = dset.MNIST(root=root, train=True, transform=trans, download=True)
test_set = dset.MNIST(root=root, train=False, transform=trans, download=True)

batch_size = 100

train_loader = torch.utils.data.DataLoader(
    dataset=train_set, batch_size=batch_size, shuffle=True
)
test_loader = torch.utils.data.DataLoader(
    dataset=test_set, batch_size=batch_size, shuffle=False
) 

print("Total training batches: {}".format(len(train_loader)))
print("Total testing batches: {}".format(len(test_loader)))

# Define the network
class LeNet(nn.Module):
    def __init__(self):
        super(LeNet, self).__init__()
        self.conv1 = nn.Conv2d(1, 20, 5, 1)
        self.conv2 = nn.Conv2d(20, 50, 5, 1)
        self.fc1 = nn.Linear(4 * 4 * 50, 500)
        self.fc2 = nn.Linear(500, 10)

    def forward(self, x): 
        x = F.relu(self.conv1(x))
        x = F.max_pool2d(x, 2, 2)
        x = F.relu(self.conv2(x))
        x = F.max_pool2d(x, 2, 2)
        x = x.view(-1, 4 * 4 * 50)
        x = F.relu(self.fc1(x))
        x = self.fc2(x)
        return x

    def name(self):
        return "LeNet"

# Train the model
model = LeNet()

optimizer = optim.SGD(model.parameters(), lr=0.01, momentum=0.9)

criterion = nn.CrossEntropyLoss()

for epoch in range(1):
    # Model training
    ave_loss = 0
    for batch_idx, (x, target) in enumerate(train_loader):
        optimizer.zero_grad()
        x, target = Variable(x), Variable(target)
        out = model(x)
        loss = criterion(out, target)
        ave_loss = (ave_loss * batch_idx + loss.item()) / (batch_idx + 1)
        loss.backward()
        optimizer.step()
        if (batch_idx + 1) % 100 == 0 or (batch_idx + 1) == len(train_loader):
            print(
                "==>>> epoch: {}, batch index: {}, train loss: {:.6f}".format(
                    epoch, batch_idx + 1, ave_loss
                )
            )
    # Model testing
    correct_cnt, total_cnt, ave_loss = 0, 0, 0
    for batch_idx, (x, target) in enumerate(test_loader):
        x, target = Variable(x, volatile=True), Variable(target, volatile=True)
        out = model(x)
        loss = criterion(out, target)
        _, pred_label = torch.max(out.data, 1)
        total_cnt += x.data.size()[0]
        correct_cnt += (pred_label == target.data).sum()
        ave_loss = (ave_loss * batch_idx + loss.item()) / (batch_idx + 1)

        if (batch_idx + 1) % 100 == 0 or (batch_idx + 1) == len(test_loader):
            print(
                "==>>> epoch: {}, batch index: {}, test loss: {:.6f}, acc: {:.3f}".format(
                    epoch, batch_idx + 1, ave_loss, correct_cnt * 1.0 / total_cnt
                )
            )

torch.save(model.state_dict(), model.name())

Log a model with MLflow

Start an MLflow run to log results in the machine learning experiment. The code registers a new model named sample-pytorch in the sample-pytorch experiment.

Run this code to log the model:

with mlflow.start_run() as run:
    print("log pytorch model:")
    mlflow.pytorch.log_model(
        model, "pytorch-model", registered_model_name="sample-pytorch"
    )

    model_uri = "runs:/{}/pytorch-model".format(run.info.run_id)
    print("Model saved in run %s" % run.info.run_id)
    print(f"Model URI: {model_uri}")

Load and evaluate the model

After you save the model, load it for inference.

Run this code in your notebook to load the model and run inference:

# Load the logged model for inference

loaded_model = mlflow.pytorch.load_model(model_uri)
print(type(loaded_model))

correct_cnt, total_cnt, ave_loss = 0, 0, 0
for batch_idx, (x, target) in enumerate(test_loader):
    x, target = Variable(x, volatile=True), Variable(target, volatile=True)
    out = loaded_model(x)
    loss = criterion(out, target)
    _, pred_label = torch.max(out.data, 1)
    total_cnt += x.data.size()[0]
    correct_cnt += (pred_label == target.data).sum()
    ave_loss = (ave_loss * batch_idx + loss.item()) / (batch_idx + 1)

    if (batch_idx + 1) % 100 == 0 or (batch_idx + 1) == len(test_loader):
        print(
            "==>>> epoch: {}, batch index: {}, test loss: {:.6f}, acc: {:.3f}".format(
                epoch, batch_idx + 1, ave_loss, correct_cnt * 1.0 / total_cnt
            )
        )

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