mmlearn

This project aims at enabling the evaluation of existing multimodal representation learning methods, as well as facilitating experimentation and research for new techniques.

Quick Start

Installation

Prerequisites

The library requires Python 3.10 or later. We recommend using a virtual environment to manage dependencies. You can create a virtual environment using the following command:

python3 -m venv /path/to/new/virtual/environment
source /path/to/new/virtual/environment/bin/activate

Installing binaries

To install the pre-built binaries, run:

python3 -m pip install mmlearn

Installation Options

You can install optional dependencies to enable additional features. Use one or more of the pip extras listed below to install the desired dependencies.

pip extra	Dependencies	Notes
vision	"torchvision", "opencv-python", "timm"	Enables image processing and vision tasks.
audio	"torchaudio"	Enables audio processing and tasks.
peft	"peft"	Uses the PEFT library to enable parameter-efficient fine-tuning.

For example, to install the library with the vision and audio extras, run:

python3 -m pip install mmlearn[vision,audio]

Building from source

To install the library from source, run:

git clone https://github.com/VectorInstitute/mmlearn.git
cd mmlearn
python3 -m pip install -e .

Running Experiments

We use Hydra and hydra-zen to manage configurations in the library.

For new experiments, it is recommended to create a new directory to store the configuration files. The directory should have an __init__.py file to make it a Python package and an experiment folder to store the experiment configuration files. This format allows the use of .yaml configuration files as well as Python modules (using structured configs or hydra-zen) to define the experiment configurations.

To run an experiment, use the following command:

mmlearn_run 'hydra.searchpath=[pkg://path.to.config.directory]' +experiment=<name_of_experiment_yaml_file> experiment=your_experiment_name

Hydra will compose the experiment configuration from all the configurations in the specified directory as well as all the configurations in the mmlearn package. Note the dot-separated path to the directory containing the experiment configuration files. One can add a path to hydra.searchpath either as a package (pkg://path.to.config.directory) or as a file system (file://path/to/config/directory). However, new configs in mmlearn are added to hydra's external store inside path/to/config/directory/__init__.py which is only interpreted when the config directory is added as a package. Hence, please refrain from using the file:// notation.

Hydra also allows for overriding configurations parameters from the command line. To see the available options and other information, run:

mmlearn_run 'hydra.searchpath=[pkg://path.to.config.directory]' +experiment=<name_of_experiment_yaml_file> --help

By default, the mmlearn_run command will run the experiment locally. To run the experiment on a SLURM cluster, we use the submitit launcher plugin built into Hydra. The following is an example of how to run an experiment on a SLURM cluster:

mmlearn_run --multirun hydra.launcher.mem_gb=32 hydra.launcher.qos=your_qos hydra.launcher.partition=your_partition hydra.launcher.gres=gpu:4 hydra.launcher.cpus_per_task=8 hydra.launcher.tasks_per_node=4 hydra.launcher.nodes=1 hydra.launcher.stderr_to_stdout=true hydra.launcher.timeout_min=60 '+hydra.launcher.additional_parameters={export: ALL}' 'hydra.searchpath=[pkg://path.to.config.directory]' +experiment=<name_of_experiment_yaml_file> experiment=your_experiment_name

This will submit a job to the SLURM cluster with the specified resources.

Note: After the job is submitted, it is okay to cancel the program with Ctrl+C. The job will continue running on the cluster. You can also add & at the end of the command to run it in the background.

Summary of Implemented Methods

Pretraining Methods	Notes
Contrastive Pretraining	Uses the contrastive loss to align the representations from N modalities. Supports sharing of encoders, projection heads or postprocessing modules (e.g. logit/temperature scaling) across modalities. Also supports multi-task learning with auxiliary unimodal tasks applied to specific modalities.
Evaluation Methods	Notes
Zero-shot Cross-modal Retrieval	Evaluates the quality of the learned representations in retrieving the k most similar examples from a different modality, using recall@k metric. This is applicable to any number of pairs of modalities at once, depending on memory constraints.

Components

Datasets

Every dataset object must return an instance of Example with one or more keys/attributes corresponding to a modality name as specified in the Modalities registry. The Example object must also include an example_index attribute/key, which is used, in addition to the dataset index, to uniquely identify the example.

CombinedDataset

The CombinedDataset object is used to combine multiple datasets into one. It accepts an iterable of torch.utils.data.Dataset and/or torch.utils.data.IterableDataset objects and returns an Example object from one of the datasets, given an index. Conceptually, the CombinedDataset object is a concatenation of the datasets in the input iterable, so the given index can be mapped to a specific dataset based on the size of the datasets. As iterable-style datasets do not support random access, the examples from these datasets are returned in order as they are iterated over.

The CombinedDataset object also adds a dataset_index attribute to the Example object, corresponding to the index of the dataset in the input iterable. Every example returned by the CombinedDataset will have an example_ids attribute, which is instance of Example containing the same keys/attributes as the original example, with the exception of the example_index and dataset_index attributes, with values being a tensor of the dataset_index and example_index.

Dataloading

When dealing with multiple datasets with different modalities, the default collate_fn of torch.utils.data.DataLoader may not work, as it assumes that all examples have the same keys/attributes. In that case, the collate_example_list function can be used as the collate_fn argument of torch.utils.data.DataLoader. This function takes a list of Example objects and returns a dictionary of tensors, with all the keys/attributes of the Example objects.

Contributing

If you are interested in contributing to the library, please see CONTRIBUTING.MD. This file contains many details around contributing to the code base, including are development practices, code checks, tests, and more.