{ "cells": [ { "cell_type": "code", "execution_count": null, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "%matplotlib inline" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "\n", "`Learn the Basics `_ ||\n", "**Quickstart** ||\n", "`Tensors `_ ||\n", "`Datasets & DataLoaders `_ ||\n", "`Transforms `_ ||\n", "`Build Model `_ ||\n", "`Autograd `_ ||\n", "`Optimization `_ ||\n", "`Save & Load Model `_\n", "\n", "Quickstart\n", "===================\n", "This section runs through the API for common tasks in machine learning. Refer to the links in each section to dive deeper.\n", "\n", "Working with data\n", "-----------------\n", "PyTorch has two `primitives to work with data `_:\n", "``torch.utils.data.DataLoader`` and ``torch.utils.data.Dataset``.\n", "``Dataset`` stores the samples and their corresponding labels, and ``DataLoader`` wraps an iterable around\n", "the ``Dataset``.\n", "\n", "\n" ] }, { "cell_type": "code", "execution_count": 3, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "import torch\n", "from torch import nn\n", "from torch.utils.data import DataLoader\n", "from torchvision import datasets\n", "from torchvision.transforms import ToTensor, Lambda, Compose\n", "import matplotlib.pyplot as plt" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "PyTorch offers domain-specific libraries such as `TorchText `_,\n", "`TorchVision `_, and `TorchAudio `_,\n", "all of which include datasets. For this tutorial, we will be using a TorchVision dataset.\n", "\n", "The ``torchvision.datasets`` module contains ``Dataset`` objects for many real-world vision data like\n", "CIFAR, COCO (`full list here `_). In this tutorial, we\n", "use the FashionMNIST dataset. Every TorchVision ``Dataset`` includes two arguments: ``transform`` and\n", "``target_transform`` to modify the samples and labels respectively.\n", "\n" ] }, { "cell_type": "code", "execution_count": 4, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "# Download training data from open datasets.\n", "training_data = datasets.FashionMNIST(\n", " root=\"data\",\n", " train=True,\n", " download=True,\n", " transform=ToTensor(),\n", ")\n", "\n", "# Download test data from open datasets.\n", "test_data = datasets.FashionMNIST(\n", " root=\"data\",\n", " train=False,\n", " download=True,\n", " transform=ToTensor(),\n", ")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "We pass the ``Dataset`` as an argument to ``DataLoader``. This wraps an iterable over our dataset, and supports\n", "automatic batching, sampling, shuffling and multiprocess data loading. Here we define a batch size of 64, i.e. each element\n", "in the dataloader iterable will return a batch of 64 features and labels.\n", "\n" ] }, { "cell_type": "code", "execution_count": 6, "metadata": {}, "outputs": [ { "data": { "text/plain": [ "torchvision.datasets.mnist.FashionMNIST" ] }, "execution_count": 6, "metadata": {}, "output_type": "execute_result" } ], "source": [ "type(training_data)" ] }, { "cell_type": "code", "execution_count": 23, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Shape of X [N, C, H, W]: torch.Size([200, 1, 28, 28])\n", "Shape of y: torch.Size([200]) torch.int64\n" ] } ], "source": [ "batch_size = 200\n", "\n", "# Create data loaders.\n", "train_dataloader = DataLoader(training_data, batch_size=batch_size)\n", "test_dataloader = DataLoader(test_data, batch_size=batch_size)\n", "\n", "for X, y in test_dataloader:\n", " print(\"Shape of X [N, C, H, W]: \", X.shape)\n", " print(\"Shape of y: \", y.shape, y.dtype)\n", " break" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Read more about `loading data in PyTorch `_.\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "--------------\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Creating Models\n", "------------------\n", "To define a neural network in PyTorch, we create a class that inherits\n", "from `nn.Module `_. We define the layers of the network\n", "in the ``__init__`` function and specify how data will pass through the network in the ``forward`` function. To accelerate\n", "operations in the neural network, we move it to the GPU if available.\n", "\n" ] }, { "cell_type": "code", "execution_count": 24, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Using cpu device\n", "NeuralNetwork(\n", " (flatten): Flatten(start_dim=1, end_dim=-1)\n", " (linear_relu_stack): Sequential(\n", " (0): Linear(in_features=784, out_features=1024, bias=True)\n", " (1): ReLU()\n", " (2): Linear(in_features=1024, out_features=1024, bias=True)\n", " (3): ReLU()\n", " (4): Linear(in_features=1024, out_features=10, bias=True)\n", " (5): ReLU()\n", " )\n", ")\n" ] } ], "source": [ "# Get cpu or gpu device for training.\n", "device = \"cuda\" if torch.cuda.is_available() else \"cpu\"\n", "print(\"Using {} device\".format(device))\n", "\n", "# Define model\n", "class NeuralNetwork(nn.Module):\n", " def __init__(self):\n", " super(NeuralNetwork, self).__init__()\n", " self.flatten = nn.Flatten()\n", " self.linear_relu_stack = nn.Sequential(\n", " nn.Linear(28*28, 1024),\n", " nn.ReLU(),\n", " nn.Linear(1024, 1024),\n", " nn.ReLU(),\n", " nn.Linear(1024, 10),\n", " nn.ReLU()\n", " )\n", "\n", " def forward(self, x):\n", " x = self.flatten(x)\n", " logits = self.linear_relu_stack(x)\n", " return logits\n", "\n", "model = NeuralNetwork().to(device)\n", "print(model)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Read more about `building neural networks in PyTorch `_.\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "--------------\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Optimizing the Model Parameters\n", "----------------------------------------\n", "To train a model, we need a `loss function `_\n", "and an `optimizer `_.\n", "\n" ] }, { "cell_type": "code", "execution_count": 25, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "loss_fn = nn.CrossEntropyLoss()\n", "optimizer = torch.optim.SGD(model.parameters(), lr=1e-3)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "In a single training loop, the model makes predictions on the training dataset (fed to it in batches), and\n", "backpropagates the prediction error to adjust the model's parameters.\n", "\n" ] }, { "cell_type": "code", "execution_count": 27, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "def train(dataloader, model, loss_fn, optimizer):\n", " size = len(dataloader.dataset)\n", " for batch, (X, y) in enumerate(dataloader):\n", " X, y = X.to(device), y.to(device)\n", "\n", " # Compute prediction error\n", " pred = model(X)\n", " loss = loss_fn(pred, y)\n", "\n", " # Backpropagation\n", " optimizer.zero_grad()\n", " loss.backward()\n", " optimizer.step()\n", "\n", " if batch % 100 == 0:\n", " loss, current = loss.item(), batch * len(X)\n", " print(f\"loss: {loss:>7f} [{current:>5d}/{size:>5d}]\")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "We also check the model's performance against the test dataset to ensure it is learning.\n", "\n" ] }, { "cell_type": "code", "execution_count": 28, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [], "source": [ "def test(dataloader, model, loss_fn):\n", " size = len(dataloader.dataset)\n", " num_batches = len(dataloader)\n", " model.eval()\n", " test_loss, correct = 0, 0\n", " with torch.no_grad():\n", " for X, y in dataloader:\n", " X, y = X.to(device), y.to(device)\n", " pred = model(X)\n", " test_loss += loss_fn(pred, y).item()\n", " correct += (pred.argmax(1) == y).type(torch.float).sum().item()\n", " test_loss /= num_batches\n", " correct /= size\n", " print(f\"Test Error: \\n Accuracy: {(100*correct):>0.1f}%, Avg loss: {test_loss:>8f} \\n\")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "The training process is conducted over several iterations (*epochs*). During each epoch, the model learns\n", "parameters to make better predictions. We print the model's accuracy and loss at each epoch; we'd like to see the\n", "accuracy increase and the loss decrease with every epoch.\n", "\n" ] }, { "cell_type": "code", "execution_count": 29, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Epoch 1\n", "-------------------------------\n", "loss: 2.301592 [ 0/60000]\n", "loss: 2.289894 [20000/60000]\n", "loss: 2.280160 [40000/60000]\n", "Test Error: \n", " Accuracy: 30.9%, Avg loss: 2.269258 \n", "\n", "Epoch 2\n", "-------------------------------\n", "loss: 2.268190 [ 0/60000]\n", "loss: 2.259592 [20000/60000]\n", "loss: 2.251709 [40000/60000]\n", "Test Error: \n", " Accuracy: 34.5%, Avg loss: 2.238048 \n", "\n", "Epoch 3\n", "-------------------------------\n", "loss: 2.236049 [ 0/60000]\n", "loss: 2.230108 [20000/60000]\n", "loss: 2.223023 [40000/60000]\n", "Test Error: \n", " Accuracy: 34.4%, Avg loss: 2.204923 \n", "\n", "Epoch 4\n", "-------------------------------\n", "loss: 2.201698 [ 0/60000]\n", "loss: 2.199297 [20000/60000]\n", "loss: 2.192280 [40000/60000]\n", "Test Error: \n", " Accuracy: 34.7%, Avg loss: 2.168218 \n", "\n", "Epoch 5\n", "-------------------------------\n", "loss: 2.163056 [ 0/60000]\n", "loss: 2.165860 [20000/60000]\n", "loss: 2.158360 [40000/60000]\n", "Test Error: \n", " Accuracy: 35.1%, Avg loss: 2.126790 \n", "\n", "Epoch 6\n", "-------------------------------\n", "loss: 2.118984 [ 0/60000]\n", "loss: 2.128839 [20000/60000]\n", "loss: 2.120741 [40000/60000]\n", "Test Error: \n", " Accuracy: 35.5%, Avg loss: 2.080902 \n", "\n", "Epoch 7\n", "-------------------------------\n", "loss: 2.069693 [ 0/60000]\n", "loss: 2.088246 [20000/60000]\n", "loss: 2.080452 [40000/60000]\n", "Test Error: \n", " Accuracy: 35.9%, Avg loss: 2.032795 \n", "\n", "Epoch 8\n", "-------------------------------\n", "loss: 2.017604 [ 0/60000]\n", "loss: 2.045965 [20000/60000]\n", "loss: 2.040246 [40000/60000]\n", "Test Error: \n", " Accuracy: 36.2%, Avg loss: 1.986216 \n", "\n", "Epoch 9\n", "-------------------------------\n", "loss: 1.966350 [ 0/60000]\n", "loss: 2.004781 [20000/60000]\n", "loss: 2.002753 [40000/60000]\n", "Test Error: \n", " Accuracy: 36.6%, Avg loss: 1.944349 \n", "\n", "Epoch 10\n", "-------------------------------\n", "loss: 1.919495 [ 0/60000]\n", "loss: 1.967277 [20000/60000]\n", "loss: 1.969415 [40000/60000]\n", "Test Error: \n", " Accuracy: 37.1%, Avg loss: 1.908297 \n", "\n", "Epoch 11\n", "-------------------------------\n", "loss: 1.878579 [ 0/60000]\n", "loss: 1.934277 [20000/60000]\n", "loss: 1.940233 [40000/60000]\n", "Test Error: \n", " Accuracy: 38.0%, Avg loss: 1.877542 \n", "\n", "Epoch 12\n", "-------------------------------\n", "loss: 1.843474 [ 0/60000]\n", "loss: 1.905277 [20000/60000]\n", "loss: 1.914412 [40000/60000]\n", "Test Error: \n", " Accuracy: 38.9%, Avg loss: 1.850760 \n", "\n", "Epoch 13\n", "-------------------------------\n", "loss: 1.812682 [ 0/60000]\n", "loss: 1.879232 [20000/60000]\n", "loss: 1.890868 [40000/60000]\n", "Test Error: \n", " Accuracy: 39.6%, Avg loss: 1.826784 \n", "\n", "Epoch 14\n", "-------------------------------\n", "loss: 1.785155 [ 0/60000]\n", "loss: 1.855434 [20000/60000]\n", "loss: 1.868896 [40000/60000]\n", "Test Error: \n", " Accuracy: 40.1%, Avg loss: 1.804814 \n", "\n", "Epoch 15\n", "-------------------------------\n", "loss: 1.760130 [ 0/60000]\n", "loss: 1.833383 [20000/60000]\n", "loss: 1.848235 [40000/60000]\n", "Test Error: \n", " Accuracy: 40.5%, Avg loss: 1.784439 \n", "\n", "Epoch 16\n", "-------------------------------\n", "loss: 1.737113 [ 0/60000]\n", "loss: 1.812643 [20000/60000]\n", "loss: 1.828667 [40000/60000]\n", "Test Error: \n", " Accuracy: 40.9%, Avg loss: 1.765419 \n", "\n", "Epoch 17\n", "-------------------------------\n", "loss: 1.715825 [ 0/60000]\n", "loss: 1.792752 [20000/60000]\n", "loss: 1.809863 [40000/60000]\n", "Test Error: \n", " Accuracy: 41.2%, Avg loss: 1.747591 \n", "\n", "Epoch 18\n", "-------------------------------\n", "loss: 1.695961 [ 0/60000]\n", "loss: 1.773857 [20000/60000]\n", "loss: 1.791943 [40000/60000]\n", "Test Error: \n", " Accuracy: 41.5%, Avg loss: 1.723384 \n", "\n", "Epoch 19\n", "-------------------------------\n", "loss: 1.669920 [ 0/60000]\n", "loss: 1.726300 [20000/60000]\n", "loss: 1.758728 [40000/60000]\n", "Test Error: \n", " Accuracy: 42.2%, Avg loss: 1.677625 \n", "\n", "Epoch 20\n", "-------------------------------\n", "loss: 1.626003 [ 0/60000]\n", "loss: 1.674431 [20000/60000]\n", "loss: 1.733464 [40000/60000]\n", "Test Error: \n", " Accuracy: 43.5%, Avg loss: 1.645380 \n", "\n", "Done!\n" ] } ], "source": [ "epochs = 20\n", "for t in range(epochs):\n", " print(f\"Epoch {t+1}\\n-------------------------------\")\n", " train(train_dataloader, model, loss_fn, optimizer)\n", " test(test_dataloader, model, loss_fn)\n", "print(\"Done!\")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Read more about `Training your model `_.\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "--------------\n", "\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Saving Models\n", "-------------\n", "A common way to save a model is to serialize the internal state dictionary (containing the model parameters).\n", "\n" ] }, { "cell_type": "code", "execution_count": 9, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Saved PyTorch Model State to model.pth\n" ] } ], "source": [ "torch.save(model.state_dict(), \"model.pth\")\n", "print(\"Saved PyTorch Model State to model.pth\")" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "Loading Models\n", "----------------------------\n", "\n", "The process for loading a model includes re-creating the model structure and loading\n", "the state dictionary into it.\n", "\n" ] }, { "cell_type": "code", "execution_count": 10, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "data": { "text/plain": [ "" ] }, "execution_count": 10, "metadata": {}, "output_type": "execute_result" } ], "source": [ "model = NeuralNetwork()\n", "model.load_state_dict(torch.load(\"model.pth\"))" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "This model can now be used to make predictions.\n", "\n" ] }, { "cell_type": "code", "execution_count": 22, "metadata": { "collapsed": false, "jupyter": { "outputs_hidden": false } }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Predicted: \"Sandal\", Actual: \"Ankle boot\"\n", "Predicted: \"Shirt\", Actual: \"Pullover\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Shirt\", Actual: \"Shirt\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Shirt\", Actual: \"Coat\"\n", "Predicted: \"Shirt\", Actual: \"Shirt\"\n", "Predicted: \"Sneaker\", Actual: \"Sandal\"\n", "Predicted: \"Sneaker\", Actual: \"Sneaker\"\n", "Predicted: \"T-shirt/top\", Actual: \"Coat\"\n", "Predicted: \"Sandal\", Actual: \"Sandal\"\n", "Predicted: \"Sandal\", Actual: \"Sneaker\"\n", "Predicted: \"Dress\", Actual: \"Dress\"\n", "Predicted: \"Shirt\", Actual: \"Coat\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Shirt\", Actual: \"Pullover\"\n", "Predicted: \"Shirt\", Actual: \"Coat\"\n", "Predicted: \"Bag\", Actual: \"Bag\"\n", "Predicted: \"T-shirt/top\", Actual: \"T-shirt/top\"\n", "Predicted: \"Shirt\", Actual: \"Pullover\"\n", "Predicted: \"Sneaker\", Actual: \"Sandal\"\n", "Predicted: \"Sneaker\", Actual: \"Sneaker\"\n", "Predicted: \"Sneaker\", Actual: \"Ankle boot\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Shirt\", Actual: \"Coat\"\n", "Predicted: \"Shirt\", Actual: \"Shirt\"\n", "Predicted: \"Dress\", Actual: \"T-shirt/top\"\n", "Predicted: \"Sandal\", Actual: \"Ankle boot\"\n", "Predicted: \"Dress\", Actual: \"Dress\"\n", "Predicted: \"Bag\", Actual: \"Bag\"\n", "Predicted: \"Bag\", Actual: \"Bag\"\n", "Predicted: \"Dress\", Actual: \"Dress\"\n", "Predicted: \"Dress\", Actual: \"Dress\"\n", "Predicted: \"Bag\", Actual: \"Bag\"\n", "Predicted: \"T-shirt/top\", Actual: \"T-shirt/top\"\n", "Predicted: \"Sneaker\", Actual: \"Sneaker\"\n", "Predicted: \"Sandal\", Actual: \"Sandal\"\n", "Predicted: \"Sneaker\", Actual: \"Sneaker\"\n", "Predicted: \"T-shirt/top\", Actual: \"Ankle boot\"\n", "Predicted: \"T-shirt/top\", Actual: \"Shirt\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Dress\", Actual: \"Dress\"\n", "Predicted: \"Sneaker\", Actual: \"Sneaker\"\n", "Predicted: \"Shirt\", Actual: \"Shirt\"\n", "Predicted: \"Sandal\", Actual: \"Sneaker\"\n", "Predicted: \"Shirt\", Actual: \"Pullover\"\n", "Predicted: \"Trouser\", Actual: \"Trouser\"\n", "Predicted: \"Trouser\", Actual: \"Pullover\"\n", "Predicted: \"Shirt\", Actual: \"Pullover\"\n" ] } ], "source": [ "classes = [\n", " \"T-shirt/top\",\n", " \"Trouser\",\n", " \"Pullover\",\n", " \"Dress\",\n", " \"Coat\",\n", " \"Sandal\",\n", " \"Shirt\",\n", " \"Sneaker\",\n", " \"Bag\",\n", " \"Ankle boot\",\n", "]\n", "\n", "model.eval()\n", "for i in range(0, 50):\n", " x, y = test_data[i][0], test_data[i][1]\n", " with torch.no_grad():\n", " pred = model(x)\n", " predicted, actual = classes[pred[0].argmax(0)], classes[y]\n", " print(f'Predicted: \"{predicted}\", Actual: \"{actual}\"')" ] }, { "cell_type": "code", "execution_count": null, "metadata": {}, "outputs": [], "source": [] } ], "metadata": { "kernelspec": { "display_name": "PyTorch", "language": "python", "name": "pytorch" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.9.6" } }, "nbformat": 4, "nbformat_minor": 4 }