Deconstructing Lottery Tickets: Zeros, Signs, and the Supermask

Authors

Hattie Zhou, Janice Lan, Rosanne Liu, Jason Yosinski

Introduction

This codebase implements the experiments in Deconstructing Lottery Tickets: Zeros, Signs, and the Supermask. This paper performs various ablation studies to shine light into the Lottery Tickets (LT) phenomenon observed by Frankle & Carbin in The Lottery Ticket Hypothesis: Finding Small, Trainable Neural Networks.

@inproceedings{zhou_2019_dlt
  title={Deconstructing Lottery Tickets: Zeros, Signs, and the Supermask},
  author={Zhou, Hattie and Lan, Janice and Liu, Rosanne and Yosinski, Jason},
  booktitle={Advances in Neural Information Processing Systems},
  year={2019}
}

For more on this project, see the Uber Eng Blog post.

Codebase structure

• data/download_mnist.py, data/download_cifar10.py downloads MNIST/CIFAR10 data and splits it into train, val, and test, and saves them in the data folder as h5 files
• get_weight_init.py computes various mask criteria
• masked_layers.py defines new layer classes with masking options
• masked_networks.py defines new layers and networks used in training Supermasks
• network_builders.py defines the four network architecture evaluated in the paper (FC, Conv2, Conv4, Conv6)
• train.py trains original unmasked networks
• train_lottery.py reads in initial and final weights from a previously trained model, calculates the mask, and train a lottery style network
• train_supermask trains a supermask directly using Bernoulli sampling
• get_init_loss_train_lottery.py derives masks and calculates the initial accuracy of the masked network for various pruning percentages and mask criteria. Note that this uses a one-shot approach rather than an iterative approach.

This codebase uses the GitResultsManager package to keep track of experiments. See: https://github.com/yosinski/GitResultsManager

Example commands for running experiments

The following commands provide examples for running experiments in Deconstructing Lottery Tickets.

Train the original, unpruned network

• Train a FC network (300-100-10) on MNIST: ./print_train_command.sh iter fc test 0 t

Alternative mask criteria experiments (using FC on MNIST and large final as an example)

• Perform iterative LT training for a FC network on MNIST using large final mask criterion: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 mask none t

Mask-1 experiments

• Randomly reinitialize weights prior to each round of iterative retraining: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 mask random_reinit t

• Randomly reshuffle the initial values of remaining weights prior to each round of iterative retraining: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 mask random_reshuffle t

• Convert the initial values of weights to a signed constant before randomly reshuffle the initial values of remaining weights prior to each round of iterative retraining: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 mask rand_signed_constant t

• For versions that maintain the same sign, see signed_reinit, signed_reshuffle, and signed_constant.

Mask-0 experiments

• Freeze pruned weights at initial values: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 freeze_init none t

• Freeze pruned weights that increased in magnitude at initial values: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 freeze_init_zero_mask none t

• Initialize weights that decreased in magnitude at 0, and freeze pruned weights at initial value: ./print_train_lottery_iterative_command.sh fc test 0 large_final -1 freeze_init_zero_all none t

Supermask experiments

• Evaluate the initial test accuracy of all alternative mask criteria: python get_init_loss_train_lottery.py --output_dir ./results/iter_lot_fc_orig/test_seed_0/ --train_h5 ./data/mnist_train.h5 --test_h5 ./data/mnist_test.h5 --arch fc_lot --seed 0 --opt adam --lr 0.0012 --exp none --layer_cutoff 4,6 --prune_base 0.8,0.9 --prune_power 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24

• Train a Supermask directly: python train_supermask.py --output_dir ./results/iter_lot_fc_orig/learned_supermasks/run1/ --train_h5 ./data/mnist_train.h5 --test_h5 ./data/mnist_test.h5 --arch fc_mask --opt sgd --lr 100 --num_epochs 2000 --print_every 220 --eval_every 220 --log_every 220 --save_weights --save_every 22000