[Re] Domain Generalization using Causal Matching

RICHARD D JILES, Mohna Chakraborty

Keywords: domain, generalization, resnet, machine, learning, neural, network, medical, xray, image, data

TL;DR: The results of the original paper were replicated with a few variances.

Abstract:

Scope of Reproducibility
We reproduced the results of the paper "Domain Generalization Using Causal Matching." Traditional supervised
learning assumes that the classes/labels seen in testing must have appeared during the training phase. However, this
assumption is often violated in real-world applications. For instance, in e-commerce, new categories of products are
released every day. A model that cannot detect new/unseen classes is hard to function in such open environments as
they are not generalizable.

Methodology
The open-source code of the paper has been used. The authors provided detailed instructions to reproduce the results on
their GitHub page. We reproduced almost every table in the main text and few of them from the appendix. In case of a
mismatch of the results, we also investigated the cause and proposed possible explanations for such behavior. For the
extensions, we wrote extra functions to check the paper’s claim on other open-source standard datasets. We mainly
used the infrastructure offered by the publicly available GPUs offered by Google Colab and GPU-assisted desktop
computers to train the models.

Results
Most of our results closely match the reported results in the original paper for the Rotated-MNIST [17], Fashion-MNIST
[27], PACS [18, 28], and Chest-Xray [3] datasets. However, in some cases, as described later, we obtained better results
quantitatively than the ones reported in the paper. By investigating the root cause of such mismatches, we provide a
possible reason to avoid such a gap. We performed additional experiments by making necessary modifications for the
Rotated-MNIST and Rotated Fashion-MNIST dataset. In general, our results still support the main claim of the original
paper, even though the results differ for some of the training/testing instances.

What was easy
The official GitHub page of the paper has the open-source code, which was beneficial as it was well organized into
multiple files. Thus, it was easy to follow. The experiments described in the paper were done on widely-used standard
open-source datasets. Therefore, implementing each experiment was relatively easy to do. Furthermore, since most of
the parameters were reported in the scripts, we did not need much tuning in most experiments.

What was difficult
Though implementing each experiment is relatively simple, the numerosity of experiments was a hard task. In particular,
each experiment in the original setting requires training a network for a significant number of iterations. Having limited
access to computational resources and time, we sometimes changed the settings, sacrificing granularity. However, these
changes did not affect the interpretability of the final results.

Communication with original authors
We emailed the authors and received prompt responses to our questions regarding the provided Jupyter reproduction
notebooks. Some tables had multiple runs for the same technique, but it was unclear how to execute the alternative runs

Paper Url: https://arxiv.org/pdf/2006.07500.pdf

Paper Venue: ICML 2021

Community Implementations: [ 4 code implementations](https://www.catalyzex.com/paper/domain-generalization-using-causal-matching/code)