24,160 research outputs found
Network unfairness in dragonfly topologies
Dragonfly networks arrange network routers in a two-level hierarchy, providing a competitive cost-performance solution for large systems. Non-minimal adaptive routing (adaptive misrouting) is employed to fully exploit the path diversity and increase the performance under adversarial traffic patterns. Network fairness issues arise in the dragonfly for several combinations of traffic pattern, global misrouting and traffic prioritization policy. Such unfairness prevents a balanced use of the resources across the network nodes and degrades severely the performance of any application running on an affected node. This paper reviews the main causes behind network unfairness in dragonflies, including a new adversarial traffic pattern which can easily occur in actual systems and congests all the global output links of a single router. A solution for the observed unfairness is evaluated using age-based arbitration. Results show that age-based arbitration mitigates fairness issues, especially when using in-transit adaptive routing. However, when using source adaptive routing, the saturation of the new traffic pattern interferes with the mechanisms employed to detect remote congestion, and the problem grows with the network size. This makes source adaptive routing in dragonflies based on remote notifications prone to reduced performance, even when using age-based arbitration.Peer ReviewedPostprint (author's final draft
Ethical Adversaries: Towards Mitigating Unfairness with Adversarial Machine Learning
Machine learning is being integrated into a growing number of critical
systems with far-reaching impacts on society. Unexpected behaviour and unfair
decision processes are coming under increasing scrutiny due to this widespread
use and its theoretical considerations. Individuals, as well as organisations,
notice, test, and criticize unfair results to hold model designers and
deployers accountable. We offer a framework that assists these groups in
mitigating unfair representations stemming from the training datasets. Our
framework relies on two inter-operating adversaries to improve fairness. First,
a model is trained with the goal of preventing the guessing of protected
attributes' values while limiting utility losses. This first step optimizes the
model's parameters for fairness. Second, the framework leverages evasion
attacks from adversarial machine learning to generate new examples that will be
misclassified. These new examples are then used to retrain and improve the
model in the first step. These two steps are iteratively applied until a
significant improvement in fairness is obtained. We evaluated our framework on
well-studied datasets in the fairness literature -- including COMPAS -- where
it can surpass other approaches concerning demographic parity, equality of
opportunity and also the model's utility. We also illustrate our findings on
the subtle difficulties when mitigating unfairness and highlight how our
framework can assist model designers.Comment: 15 pages, 3 figures, 1 tabl
FNNC: Achieving Fairness through Neural Networks
In classification models fairness can be ensured by solving a constrained
optimization problem. We focus on fairness constraints like Disparate Impact,
Demographic Parity, and Equalized Odds, which are non-decomposable and
non-convex. Researchers define convex surrogates of the constraints and then
apply convex optimization frameworks to obtain fair classifiers. Surrogates
serve only as an upper bound to the actual constraints, and convexifying
fairness constraints might be challenging.
We propose a neural network-based framework, \emph{FNNC}, to achieve fairness
while maintaining high accuracy in classification. The above fairness
constraints are included in the loss using Lagrangian multipliers. We prove
bounds on generalization errors for the constrained losses which asymptotically
go to zero. The network is optimized using two-step mini-batch stochastic
gradient descent. Our experiments show that FNNC performs as good as the state
of the art, if not better. The experimental evidence supplements our
theoretical guarantees. In summary, we have an automated solution to achieve
fairness in classification, which is easily extendable to many fairness
constraints
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