Deep Network Quantizer

Quantize a deep neural network to 8-bit scaled integer data types

Description

Use the Deep Network Quantizer app to reduce the memory requirement of a deep neural network by quantizing weights, biases, and activations of convolution layers to 8-bit scaled integer data types. Using this app you can:

  • Visualize the dynamic ranges of convolution layers in a deep neural network.

  • Select individual network layers to quantize.

  • Asses the performance of a quantized network.

  • Generate GPU code to deploy the quantized network using GPU Coder.

Quantization of a neural network requires a GPU, the GPU Coder™ Interface for Deep Learning Libraries support package, and the Deep Learning Toolbox™ Model Quantization Library support package. Using a GPU requires a CUDA® enabled NVIDIA® GPU with compute capability 6.1 or higher.

Deep Network Quantizer app

Open the Deep Network Quantizer App

  • MATLAB® command prompt: Enter deepNetworkQuantizer.

Examples

expand all

  1. Load the network to quantize into the base workspace.

    net
    net = 
    
      DAGNetwork with properties:
    
             Layers: [68x1 nnet.cnn.layer.Layer]
        Connections: [75x2 table]
         InputNames: {'data'}
        OutputNames: {'new_classoutput'}
  2. Define calibration and validation data.

    The app uses calibration data to exercise the network and collect the dynamic ranges of the weights and biases in the convolution and fully connected layers of the network and the dynamic ranges of the activations in all layers of the network. For the best quantization results, the calibration data must be representative of inputs to the network.

    The app uses the validation data to test the network after quantization to understand the effects of the limited range and precision of the quantized learnable parameters of the convolution layers in the network.

    In this example, use the images in the MerchData data set. Define an augmentedImageDatastore object to resize the data for the network. Then, split the data into calibration and validation data sets.

    unzip('MerchData.zip');
    imds = imageDatastore('MerchData', ...
        'IncludeSubfolders',true, ...
        'LabelSource','foldernames');
    [calData, valData] = splitEachLabel(imds, 0.7, 'randomized');
    aug_calData = augmentedImageDatastore([227 227], calData);
    aug_valData = augmentedImageDatastore([227 227], valData);
  3. At the MATLAB command prompt, open the app.

    deepNetworkQuantizer
  4. In the app, click the New button. The app verifies your execution environment. To use the Deep Network Quantizer app, you must have a GPU execution environment. If there is no GPU available, this step produces an error.

  5. In the dialog, select the network to quantize from the base workspace.

    Select a network

    After selecting the network, the app displays the layer graph of the network.

  6. In the Calibrate section of the toolstrip, under Calibration Data, select the augmentedImageDatastore object from the base workspace containing the calibration data, calData.

  7. Click Calibrate.

    The Deep Network Quantizer uses the calibration data to exercise the network and collect range information for the learnable parameters in the network layers.

    When the calibration is complete, the app displays a table containing the weights and biases in the convolution and fully connected layers of the network and the dynamic ranges of the activations in all layers of the network and their minimum and maximum values during the calibration. To the right of the table, the app displays histograms of the dynamic ranges of the parameters. The gray regions of the histograms indicate data that cannot be represented by the quantized representation. For more information on how to interpret these histograms, see Quantization of Deep Neural Networks.

    Deep Network Quantizer calibration

  8. In the Quantize column of the table, indicate whether to quantize the learnable parameters in the layer. Layers that are not convolution layers cannot be quantized, and therefore cannot be selected. Layers that are not quantized remain in single-precision after quantization.

  9. In the Validate section of the toolstrip, under Validation Data, select the augmentedImageDatastore object from the base workspace containing the validation data, valData.

  10. Click Quantize and Validate.

    The Deep Network Quantizer quantizes the weights, activations, and biases of convolution layers in the network to scaled 8-bit integer data types and uses the validation data to exercise the network. The app determines a metric function to use for the validation based on the type of network that is being quantized.

    Type of NetworkMetric Function
    Classification

    Top-1 Accuracy – Accuracy of the network

    Regression

    MSE – Mean squared error of the network

    When the validation is complete, the app displays the results of the validation, including:

    • Metric function used for validation

    • Result of the metric function before and after quantization

    • Memory requirement of the network before and after quantization (MB)

    Deep Network Quantizer validation

  11. After quantizing and validating the network, you can choose to export the quantized network.

    Click the Export button. In the drop down, select Export Quantizer to create a dlquantizer object in the base workspace. To open the GPU Coder app and generate GPU code from the quantized neural network, select Generate Code. Generating GPU code requires a GPU Coder license.

    If the performance of the quantized network is not satisfactory, you can choose to not quantize some layers by deselecting the layer in the table. To see the effects, click Quantize and Validate again.

Related Examples

Introduced in R2020a