vihari / CGD

Implementation of Common Gradient Descent Algorithm

CGD: A simple algotihm for robustness to sub-population shifts

Implementation of Common Gradient Descent algorithm published at ICLR 2022 (https://openreview.net/forum?id=irARV_2VFs4)

Dependencies

All the packages are documented in the environment.yaml file. Create a new conda env for reproducing results using the following command.

conda env create --file environment.yaml

Instructions for running

The code is built on WILDS codebase v1.2.2 and run on TPU v3-8. For efficiency, we only release the algorithm files and detail the minimal edits to be made on the WILDS codebase below.

1. Move the python files under algorithms to examples/algorithms of the WILDS codebase.
2. Edit examples/algorithms/initializer.py to add an import and initialization line as follows:

  from algorithms.CG import CG
  import numpy as np
  .....
    elif config.algorithm.startswith('CG'):
      train_g = train_grouper.metadata_to_group(train_dataset.metadata_array)
      is_group_in_train = get_counts(train_g, train_grouper.n_groups) > 0
      groups, u_counts = np.unique(train_g, return_counts=True)
      g_counts = np.zeros(train_grouper.n_groups)
      g_counts[groups] = u_counts

      alg = CG
      algorithm = alg(
          config=config,
          d_out=d_out,
          grouper=train_grouper,
          loss=loss,
          metric=metric,
          n_train_steps=n_train_steps,
          is_group_in_train=is_group_in_train,
          group_info=[groups, g_counts]
      )

3. Add default configuration of the algorithms to examples/configs/algorithm.py such as the following:

   'CG': {
        'train_loader': 'standard',
        'uniform_over_groups': True,
        'distinct_groups': True,
        'eval_loader': 'standard',
        'cg_step_size': 0.1
    },

4. Add the algorithm name to algorithms variable in examples/configs/supported.py.
5. Finally add to examples/run_expt.py the lines below.

parser.add_argument('--cg_C', type=float, default=0)
parser.add_argument('--cg_step_size', type=float, default=0.05)
parser.add_argument('--pgi_penalty_weight', type=float)

After the edits above, we can run using:

python run_expt.py --dataset $DATASET --algorithm $ALG --root_dir data --progress_bar --log_dir logs/"$DATASET"/$ALG/run:1:seed:"$seed" --seed $seed --weight_decay 1e-4 --n_epochs 100;

File structure

In the algorithms folder, we include implementation of our method (CGD) and Ahmed et.al. ICLR 2021.

1. CGD: algorithms/cg.py. Hyperparameters: --cg_step_size set the step size parameter and --cg_C sets the group adjustment parameter C discussed in our paper.
2. PGI (ICLR 2021): algorithms/pgi.py. Hyperparameter: --pgi_penalty_weight controls ths weight of distributional divergence discussed in their paper (lambda).

Datasets

Most of the datasets can be readily downloaded by passing --download when running run_expt.py. Additional datasets that are not part of WILDS are included in the datasets folder, these include Colored-MNIST (cmnist_debug_dataset.py) and datasets used for qualitative evaluation of Section 4 from our paper.