PyTorch/quickstart_tutorial.ipynb

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"source": [
"%matplotlib inline"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"\n",
"`Learn the Basics <intro.html>`_ ||\n",
"**Quickstart** ||\n",
"`Tensors <tensorqs_tutorial.html>`_ ||\n",
"`Datasets & DataLoaders <data_tutorial.html>`_ ||\n",
"`Transforms <transforms_tutorial.html>`_ ||\n",
"`Build Model <buildmodel_tutorial.html>`_ ||\n",
"`Autograd <autogradqs_tutorial.html>`_ ||\n",
"`Optimization <optimization_tutorial.html>`_ ||\n",
"`Save & Load Model <saveloadrun_tutorial.html>`_\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 <https://pytorch.org/docs/stable/data.html>`_:\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": {
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},
"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 <https://pytorch.org/text/stable/index.html>`_,\n",
"`TorchVision <https://pytorch.org/vision/stable/index.html>`_, and `TorchAudio <https://pytorch.org/audio/stable/index.html>`_,\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 <https://pytorch.org/vision/stable/datasets.html>`_). 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,
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"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,
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},
"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 <data_tutorial.html>`_.\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 <https://pytorch.org/docs/stable/generated/torch.nn.Module.html>`_. 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,
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}
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{
"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 <buildmodel_tutorial.html>`_.\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 <https://pytorch.org/docs/stable/nn.html#loss-functions>`_\n",
"and an `optimizer <https://pytorch.org/docs/stable/optim.html>`_.\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,
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}
},
"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": {
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}
},
"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 <optimization_tutorial.html>`_.\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": [
"<All keys matched successfully>"
]
},
"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": {
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"display_name": "PyTorch",
"language": "python",
"name": "pytorch"
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