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.. "tutorials/quantization_quick_start_mnist.py"
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.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        Click :ref:`here <sphx_glr_download_tutorials_quantization_quick_start_mnist.py>`
        to download the full example code

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_tutorials_quantization_quick_start_mnist.py:


Quantization Quickstart
=======================

Quantization reduces model size and speeds up inference time by reducing the number of bits required to represent weights or activations.

In NNI, both post-training quantization algorithms and quantization-aware training algorithms are supported.
Here we use `QAT_Quantizer` as an example to show the usage of quantization in NNI.

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Preparation
-----------

In this tutorial, we use a simple model and pre-train on MNIST dataset.
If you are familiar with defining a model and training in pytorch, you can skip directly to `Quantizing Model`_.

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.. code-block:: default


    import torch
    import torch.nn.functional as F
    from torch.optim import SGD

    from scripts.compression_mnist_model import TorchModel, trainer, evaluator, device

    # define the model
    model = TorchModel().to(device)

    # define the optimizer and criterion for pre-training

    optimizer = SGD(model.parameters(), 1e-2)
    criterion = F.nll_loss

    # pre-train and evaluate the model on MNIST dataset
    for epoch in range(3):
        trainer(model, optimizer, criterion)
        evaluator(model)





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 Out:

 .. code-block:: none

    Average test loss: 0.4877, Accuracy: 8541/10000 (85%)
    Average test loss: 0.2618, Accuracy: 9191/10000 (92%)
    Average test loss: 0.1626, Accuracy: 9543/10000 (95%)




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Quantizing Model
----------------

Initialize a `config_list`.
Detailed about how to write ``config_list`` please refer :doc:`compression config specification <../compression/compression_config_list>`.

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.. code-block:: default


    config_list = [{
        'quant_types': ['input', 'weight'],
        'quant_bits': {'input': 8, 'weight': 8},
        'op_names': ['conv1']
    }, {
        'quant_types': ['output'],
        'quant_bits': {'output': 8},
        'op_names': ['relu1']
    }, {
        'quant_types': ['input', 'weight'],
        'quant_bits': {'input': 8, 'weight': 8},
        'op_names': ['conv2']
    }, {
        'quant_types': ['output'],
        'quant_bits': {'output': 8},
        'op_names': ['relu2']
    }]








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finetuning the model by using QAT

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.. code-block:: default

    from nni.algorithms.compression.pytorch.quantization import QAT_Quantizer
    dummy_input = torch.rand(32, 1, 28, 28).to(device)
    quantizer = QAT_Quantizer(model, config_list, optimizer, dummy_input)
    quantizer.compress()
    for epoch in range(3):
        trainer(model, optimizer, criterion)
        evaluator(model)





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 Out:

 .. code-block:: none

    op_names ['relu1'] not found in model
    op_names ['relu2'] not found in model
    Average test loss: 0.1739, Accuracy: 9441/10000 (94%)
    Average test loss: 0.1078, Accuracy: 9671/10000 (97%)
    Average test loss: 0.0991, Accuracy: 9696/10000 (97%)




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export model and get calibration_config

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.. code-block:: default

    model_path = "./log/mnist_model.pth"
    calibration_path = "./log/mnist_calibration.pth"
    calibration_config = quantizer.export_model(model_path, calibration_path)

    print("calibration_config: ", calibration_config)




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 Out:

 .. code-block:: none

    calibration_config:  {'conv1': {'weight_bits': 8, 'weight_scale': tensor([0.0034], device='cuda:0'), 'weight_zero_point': tensor([75.], device='cuda:0'), 'input_bits': 8, 'tracked_min_input': -0.4242129623889923, 'tracked_max_input': 2.821486711502075}, 'conv2': {'weight_bits': 8, 'weight_scale': tensor([0.0018], device='cuda:0'), 'weight_zero_point': tensor([110.], device='cuda:0'), 'input_bits': 8, 'tracked_min_input': 0.0, 'tracked_max_input': 13.838628768920898}}





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** ( 1 minutes  51.644 seconds)


.. _sphx_glr_download_tutorials_quantization_quick_start_mnist.py:


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 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download sphx-glr-download-python

     :download:`Download Python source code: quantization_quick_start_mnist.py <quantization_quick_start_mnist.py>`



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     :download:`Download Jupyter notebook: quantization_quick_start_mnist.ipynb <quantization_quick_start_mnist.ipynb>`


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