Attention-Based Guided Structured Sparsity of Deep Neural Networks

This repository contains the code developed by TensorFlow for our paper:

Attention-Based Guided Structured Sparsity of Deep Neural Networks,
by: Amirsina Torfi and Rouzbeh Asghari Shirvani

Table of Contents

Goal and Outcome

Network pruning is aimed at imposing sparsity in a neural network architecture by increasing the portion of zero-valued weights for reducing its size energy efficiency consideration and increasing evaluation speed. In most of the conducted research efforts, the sparsity is enforced for network pruning without any attention to the internal network characteristics such as unbalanced outputs of the neurons or more specifically the distribution of the weights and outputs of the neurons. That may cause severe accuracy drop due to uncontrolled sparsity. In this work, we propose an attention mechanism that simultaneously controls the sparsity intensity and supervised network pruning by keeping important information bottlenecks of the network to be active. On CIFAR-10, the proposed method outperforms the best baseline method by 6% and reduced the accuracy drop by 2.6× at the same level of sparsity.

Scope of the works

In this work, we proposed a controller mechanism for network pruning with the goal of (1) model compression for having few active parameters by enforcing group sparsity, (2) preventing the accuracy drop by controlling the sparsity of the network using an additional loss function by forcing a portion of the output neurons to stay alive in each layer of the network, and (3) capability of being incorporated for any layer type

Requirements

TensorFLow

This code is written in Python and requires TensorFlow as the framework. For installation on Ubuntu, installing TensorFlow with GPU support can be as follows:

sudo apt-get install python3-pip python3-dev # for Python 3.n
pip3 install tensorflow-gpu

Please refer to Official TensorFLow installation guideline for further details considering your specific system architecture.

Code Implementation

dataset

For this repository, the experiments are performed on MNIST dataset which is available online. MNIST can directly be downloaded using the following script supported by TensorFLow:

from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets(FLAGS.data_dir, fake_data=FLAGS.fake_data)

For which the FLAGS are predefined by argument parser.

Architecture

In the experiment on MNIST dataset, an architecture similar to LeNet has been utilized as a baseline for investigation of our proposed method with no data augmentation. The baseline architecture has been defined as below:

def net(x,training_status):

    with tf.name_scope('reshape'):
        x_image = tf.reshape(x, [-1, 28, 28, 1])

    h_conv1 = nn_conv_layer(x_image, [5, 5, 1, 64], [64], 'conv1', \
                            training_status=training_status, act=tf.nn.relu)

    with tf.name_scope('pool1'):
        h_pool1 = max_pool_2x2(h_conv1)

    h_conv2 = nn_conv_layer(h_pool1, [5, 5, 64, 128], [128], 'conv2',\
                            training_status=training_status, act=tf.nn.relu)

    # Second pooling layer.
    with tf.name_scope('pool2'):
        h_pool2 = max_pool_2x2(h_conv2)

    h_pool2_flat = tf.reshape(h_pool2, [-1, 7 * 7 * 128])

    h_fc1 = nn_layer(h_pool2_flat, 7 * 7 * 128, 512, 'fc1', \
                     training_status=training_status, act=tf.nn.relu)
    dropped_h_fc1 = tf.nn.dropout(h_fc1, keep_prob)

    h_fc2 = nn_layer(dropped_h_fc1, 512, 256, 'fc2', \
                     training_status=training_status, act=tf.nn.relu)
    dropped_h_fc2 = tf.nn.dropout(h_fc2, keep_prob)

    # Do not apply softmax activation yet, see below.
    output = nn_layer(dropped_h_fc2, 256, 10, 'softmax', \
                      training_status=training_status, act=tf.identity)

    return output, keep_prob

Training / Evaluation

Demo

Description

At first, clone the repository. Then, cd to the dedicated directory:

cd python

Then, execute the main.py:

python main.py --max_steps=100000

Using the above script, the code does the following:

• Automatically download the dataset
• Starts training
• Does the evaluation while training is running.
• Continue training up to 100000 steps.

NOTE: If you are using a virtual environment which contains TensorFLow, make sure to activate it before running the model.

Results

The below figure depicts a comparison at different levels of sparsity. As it can be observed from the figure, our method demonstrates its superiority in higher levels of sparsity. We named our proposed method as Guided Structured Sparsity (GSS).