aloereed / dessilbi

Exploring Structural Sparsity of Deep Networks via Inverse Scale Spaces. Link

Yanwei Fu, Chen Liu, Donghao Li, Zuyuan Zhong, Xinwei Sun, Jinshan Zeng, Yuan Yao

(Extended Version of DessiLBI: Exploring Structural Sparsity of Deep Networks via Differential Inclusion Paths ICML2020)

Abstract

The great success of deep neural networks is built upon their over-parameterization, which smooths the optimization landscape without degrading the generalization ability. Despite the benefits of over-parameterization, a huge amount of parameters makes deep networks cumbersome in daily life applications. On the other hand, training neural networks without over-parameterization faces many practical problems, e.g., being trapped in local optimal. Though techniques such as pruning and distillation are developed, they are expensive in fully training a dense network as backward selection methods, and there is still a void on systematically exploring forward selection methods for learning structural sparsity in deep networks. To fill in this gap, this paper proposes a new approach based on differential inclusions of inverse scale spaces. Specifically, our method can generate a family of models from simple to complex ones along the dynamics via coupling a pair of parameters, such that over-parameterized deep models and their structural sparsity can be explored simultaneously. This kind of differential inclusion scheme has a simple discretization, dubbed Deep structure splitting Linearized Bregman Iteration (DessiLBI), whose global convergence in learning deep networks could be established under the Kurdyka-Łojasiewicz framework. Particularly, we explore several applications of DessiLBI, including finding sparse structures of networks directly via the coupled structure parameter and growing networks from simple to complex ones progressively. Experimental evidence shows that our method achieves comparable and even better performance than the competitive optimizers in exploring the sparse structure of several widely used backbones on the benchmark datasets. Remarkably, with early stopping, our method unveils “winning tickets” in early epochs: the effective sparse network structures with comparable test accuracy to fully trained over-parameterized models, that are further transferable to similar alternative tasks. Furthermore, our method is able to grow networks efficiently with adaptive filter configurations, demonstrating a good performance with much less computational cost.

Short Version

DessiLBI: Exploring Structural Sparsity of Deep Networks via Differential Inclusion Paths (ICML 2020) Link

DessiLBI

This is the project page for DessiLBI. It is an optimization toolbox for Pytorch.

Prerequisites

Pytorch 1.0 + Numpy
Python 3
CUDA

Installation

It is install-free, just put the slbi_opt.py and slbi_toolbox.py into the the project folder and import them.

Examples

We give examples for train network and prune network on MNIST dataset. These codes are in the example folder. The following codes are some usage of this toolbox.

Quick start: running an example of training a network

To train the LeNet network, please cd to the corresponding folder and just simply run

 python ./example/train/train_lenet.py  

Train your own network:

To initialize the toolbox, the following codes are needed.

from slbi_toolbox import SLBI_ToolBox
import torch
optimizer = SLBI_ToolBox(model.parameters(), lr=args.lr, kappa=args.kappa, mu=args.mu, weight_decay=0)
optimizer.assign_name(name_list)
optimizer.initialize_slbi(layer_list)

For training a neural network, the process is similar to one that uses built-in optimizer

optimizer.zero_grad()
loss.backward()
optimizer.step()

For pruning a neural network, the code is as follows.

optimizer.update_prune_order(epoch)
optimizer.prune_layer_by_order_by_list(percent, layer_name)

Pruning Network Example

This example is about Lenet using Split LBI, the code is in example/prune. We have put one pretrained model and optimizer dict in this folder. It shows the pruned results using Split LBI.
To run this demo, please download and cd to this folder and run the following code:

 python prune_lenet.py 

ImageNet Training Example

This part of code is included in example/imagenet. To do this demo, run

 python train_imagenet_slbi.py

Lottery Training Example

The part of lottery training code is included in example/lottery. To conduct this demo, please refer to the readme file under example/lottery.