Multi-task learning (MTL) aims to improve generalization performance by learning multiple related tasks simultaneously. While sometimes the underlying task relationship structure is known, often the structure needs to be estimated from data at hand. In this paper, we present a novel family of models for MTL, applicable to regression and classification problems, capable of learning the structure of tasks relationship. In particular, we consider a joint estimation problem of the tasks relationship structure and the individual task parameters, which is solved using alternating minimization. The task relationship revealed by structure learning is founded on recent advances in Gaussian graphical models endowed with sparse estimators of the precision (inverse covariance) matrix. An extension to include flexible Gaussian copula models that relaxes the Gaussian marginal assumption is also proposed. We illustrate the effectiveness of the proposed model on a variety of synthetic and benchmark data sets for regression and classification. We also consider the problem of combining Earth System Model (ESM) outputs for better projections of future climate, with focus on projections of temperature by combining ESMs in South and North America, and show that the proposed model outperforms several existing methods for the problem.
|Original language||English (US)|
|Journal||Journal of Machine Learning Research|
|State||Published - Apr 1 2016|
Bibliographical noteFunding Information:
We thank the AE and the three anonymous reviewers for their valuable comments and suggestions. The research was supported by NSF grants IIS-1029711, IIS-0916750, IIS-0953274, CNS-1314560, IIS-1422557, CCF-1451986, IIS-1447566, and by NASA grant NNX12AQ39A. AB acknowledges support from IBM and Yahoo. FJVZ thanks to CNPq for the financial support. ARG was supported by Science without Borders grant from CNPq, Brazil. Computing facilities were provided by University of Minnesota Supercomputing Institute (MSI).
- Gaussian copula
- Multi-task learning
- Probabilistic graphical model
- Sparse modeling
- Structure learning