Ridurre - Filter Pruning in Deep Convolutional Networks

Pruning is the process when we try to shrink a network by removing the not so significant/redundant filters.

This package is a mini-framework which you can easily use on your existing models and also you can define your own pruning methods without any struggle.

Install

pip install ridurre

• Install packages inside requirements.txt
  • pip install -r requirements.txt

Example Results

These results were achieved with the example provided:

• Cifar10 dataset
• ResNetV1
• KMeans filter pruning
  • Clustering factor: 0.9 (which can be considered as an aggressive pruning)

Usage

Define you own pruning method

You can make your own pruning method by creating a new class which has the parent BasePruning. There is only 1 thing you should take care and that the implementation of the run_pruning_for_conv2d_layer function.

For an example just take a look at the RandomFilterPruning code.

Use an already existing method

Check out the example/model_pruning_example.py for a simple but extensive tutorial

Callbacks

You will need to define 2 callbacks for the pruning:

• Model compile function
  • 1 argument:
    • model which is a keras.models.Model
  • This should define how to compile the model
  • Example:

    def compile_model(my_model):
        my_model.compile(optimizer=optimizers.Adam(lr=0.001),
                         loss=losses.categorical_crossentropy,
                         metrics=["accuracy"])
    

• Finetune function
  • 3 arguments:
    • model which is a keras.models.Model
    • initial_epoch which is an int: This defines the initial epoch state for the model fitting. For example it is 12 if we trained the model for 12 epochs before this function was called
    • finetune_epochs which is an int: Defines how much should we train after a pruning.
  • This should define how to finetune out model
  • Example:

    def finetune_model(my_model, initial_epoch, finetune_epochs):
            my_model.fit(x_train,
                         y_train,
                         32,
                         epochs=finetune_epochs,
                         validation_data=(x_test, y_test),
                         callbacks=callbacks,
                         initial_epoch=initial_epoch,
                         verbose=1)
    

Pruning

You will need to select which pruning method you would like to use. In this example I will use the KMeans pruning

import ridurre

# Create the model
model = build_model(...)

# Define compile callback
def compile_my_model(model):
    model.compile(...)

# Compile with your callback (of course you can use different compilation for this train and the pruning)
compile_my_model(model)

# Train if you would like to start from a better position
model.fit(...)

# Define finetuning callback
def finetune_my_model(model, initial_epoch, finetune_epochs):
    model.fit(..., epochs=finetune_epochs, initial_epoch=initial_epoch)

# We can start pruning
pruning = ridurre.KMeansFilterPruning(0.9,
                                             compile_my_model,
                                             finetune_my_model,
                                             6,
                                             maximum_pruning_percent=0.4,
                                             maximum_prune_iterations=12)
model, _ = pruning.run_pruning(model)

At the end of the pruning step, you will have a trained and pruned model which you can use. I can recommend to train your model after the pruning for just a little longer as an extra step towards accuracy.

Future work

• Look for problematic cases, where there is a merging (like add) and warn the user that the different inputs to that operations should be pruned in the same manner
  • A good example for a case like this is ResNet
• Define "pruneable" set of layers
  • With regex or layer indices
  • This needs to find add, multiply, average, etc... operations (layers) which needs same filter number from the different inputs
• Different pruning factors for channels with different number of filters
• More pruning solutions
• Do not depend on kerassurgeon as I only use the channel delete function

Papers

[1] Filter Level Pruning Based on Similar Feature Extraction for Convolutional Neural Networks

[2] Demystifying Neural Network Filter Pruning

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Gábor Vecsei

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