TaskMet: Task-Driven Metric Learning for Model Learning
Dishank Bansal Ricky T. Q. Chen Mustafa Mukadam Brandon Amos
Deep learning models are often deployed in downstream tasks that the training
procedure may not be aware of. For example, models solely trained to achieve
accurate predictions may struggle to perform well on downstream tasks because
seemingly small prediction errors may incur drastic task errors. The standard
end-to-end learning approach is to make the task loss differentiable or to
introduce a differentiable surrogate that the model can be trained on. In these
settings, the task loss needs to be carefully balanced with the prediction loss
because they may have conflicting objectives. We propose take the task loss
signal one level deeper than the parameters of the model and use it to learn
the parameters of the loss function the model is trained on, which can be done
by learning a metric in the prediction space. This approach does not alter the
optimal prediction model itself, but rather changes the model learning to
emphasize the information important for the downstream task. This enables us to
achieve the best of both worlds: a prediction model trained in the original
prediction space while also being valuable for the desired downstream task. We
validate our approach through experiments conducted in two main settings: 1)
decision-focused model learning scenarios involving portfolio optimization and
budget allocation, and 2) reinforcement learning in noisy environments with
distracting states. The source code to reproduce our experiments is available
at https://github.com/facebookresearch/taskmet