MINDS / CIS Seminar Series

Feb
11
Tue
Danilo Bzdok (hosted by CIS) @ Clark 316
Feb 11 @ 12:00 pm – 1:30 pm
Feb
25
Tue
Joshua Vogelstein @ Clark 316
Feb 25 @ 12:00 pm – 1:30 pm
Mar
2
Mon
Carlo Tomasi (hosted by CIS) @ Clark 316
Mar 2 @ 12:00 pm – 1:30 pm
Mar
24
Tue
Thomas Moreau – “Learning step sizes for unfolded sparse coding” @ Clark 316
Mar 24 @ 12:00 pm – 1:30 pm

“Learning step sizes for unfolded sparse coding”

Abstract: Sparse coding is typically solved by iterative optimization techniques, such as the Iterative Shrinkage-Thresholding Algorithm (ISTA). Unfolding and learning weights of ISTA using neural networks is a practical way to accelerate estimation. However, the reason why learning the weights of such a network would accelerate sparse coding are not clear. In this talk, we look at this problem from the point of view of selecting adapted step sizes for ISTA. We show that a simple step size strategy can improve the convergence rate of ISTA by leveraging the sparsity of the iterates. However, it is impractical in most large-scale applications. Therefore, we propose a network architecture where only the step sizes of ISTA are learned. We demonstrate if the learned algorithm converges to the solution of the Lasso, its last layers correspond to ISTA with learned step sizes. Experiments show that learning step sizes can effectively accelerate the convergence when the solutions are sparse enough.

Bio: Thomas Moreau received the graduate degree from the Ecole Polytechnique, Palaiseau, France, in 2014, and the PhD degree from the Ecole Normale Supérieure, Cachan, France, in 2017 under the supervision of Nicolas Vayatis and Laurent Oudre in the CMLA laboratory. He recently joined the Inria Parietal project team in Saclay, first as a post-doctoral researcher and then as a researcher. His research interests include unsupervised learning, image/signal processing and distributed computing.

Mar
30
Mon
James Zou (hosted by BME) @ Clark 110
Mar 30 @ 1:30 pm – 2:30 pm
Apr
7
Tue
Mihailo Jovanovic @ Clark 316
Apr 7 @ 12:00 pm – 1:30 pm
Apr
14
Tue
Stefanie Jegelka @ Clark 316
Apr 14 @ 12:00 pm – 1:30 pm
Apr
21
Tue
Tom Fletcher @ Clark 316
Apr 21 @ 12:00 pm – 1:30 pm