57,031 research outputs found
Exploiting Unlabeled Data in CNNs by Self-supervised Learning to Rank
For many applications the collection of labeled data is expensive laborious.
Exploitation of unlabeled data during training is thus a long pursued objective
of machine learning. Self-supervised learning addresses this by positing an
auxiliary task (different, but related to the supervised task) for which data
is abundantly available. In this paper, we show how ranking can be used as a
proxy task for some regression problems. As another contribution, we propose an
efficient backpropagation technique for Siamese networks which prevents the
redundant computation introduced by the multi-branch network architecture. We
apply our framework to two regression problems: Image Quality Assessment (IQA)
and Crowd Counting. For both we show how to automatically generate ranked image
sets from unlabeled data. Our results show that networks trained to regress to
the ground truth targets for labeled data and to simultaneously learn to rank
unlabeled data obtain significantly better, state-of-the-art results for both
IQA and crowd counting. In addition, we show that measuring network uncertainty
on the self-supervised proxy task is a good measure of informativeness of
unlabeled data. This can be used to drive an algorithm for active learning and
we show that this reduces labeling effort by up to 50%.Comment: Accepted at TPAMI. (Keywords: Learning from rankings, image quality
assessment, crowd counting, active learning). arXiv admin note: text overlap
with arXiv:1803.0309
Regularized Jacobi iteration for decentralized convex optimization with separable constraints
We consider multi-agent, convex optimization programs subject to separable
constraints, where the constraint function of each agent involves only its
local decision vector, while the decision vectors of all agents are coupled via
a common objective function. We focus on a regularized variant of the so called
Jacobi algorithm for decentralized computation in such problems. We first
consider the case where the objective function is quadratic, and provide a
fixed-point theoretic analysis showing that the algorithm converges to a
minimizer of the centralized problem. Moreover, we quantify the potential
benefits of such an iterative scheme by comparing it against a scaled projected
gradient algorithm. We then consider the general case and show that all limit
points of the proposed iteration are optimal solutions of the centralized
problem. The efficacy of the proposed algorithm is illustrated by applying it
to the problem of optimal charging of electric vehicles, where, as opposed to
earlier approaches, we show convergence to an optimal charging scheme for a
finite, possibly large, number of vehicles
Optimization as a design strategy. Considerations based on building simulation-assisted experiments about problem decomposition
In this article the most fundamental decomposition-based optimization method
- block coordinate search, based on the sequential decomposition of problems in
subproblems - and building performance simulation programs are used to reason
about a building design process at micro-urban scale and strategies are defined
to make the search more efficient. Cyclic overlapping block coordinate search
is here considered in its double nature of optimization method and surrogate
model (and metaphore) of a sequential design process. Heuristic indicators apt
to support the design of search structures suited to that method are developed
from building-simulation-assisted computational experiments, aimed to choose
the form and position of a small building in a plot. Those indicators link the
sharing of structure between subspaces ("commonality") to recursive
recombination, measured as freshness of the search wake and novelty of the
search moves. The aim of these indicators is to measure the relative
effectiveness of decomposition-based design moves and create efficient block
searches. Implications of a possible use of these indicators in genetic
algorithms are also highlighted.Comment: 48 pages. 12 figures, 3 table
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