5,024 research outputs found
Efficient algorithms for conditional independence inference
The topic of the paper is computer testing of (probabilistic) conditional independence (CI) implications by an algebraic method of structural imsets. The basic idea is to transform (sets of) CI statements into certain integral vectors and to verify by a computer the corresponding algebraic relation between the vectors, called the independence implication. We interpret the previous methods for computer testing of this implication from the point of view of polyhedral geometry. However, the main contribution of the paper is a new method, based on linear programming (LP). The new method overcomes the limitation of former methods to the number of involved variables. We recall/describe the theoretical basis for all four methods involved in our computational experiments, whose aim was to compare the efficiency of the algorithms. The experiments show that the LP method is clearly the fastest one. As an example of possible application of such algorithms we show that testing inclusion of Bayesian network structures or whether a CI statement is encoded in an acyclic directed graph can be done by the algebraic method
Strategic Behavior is Bliss: Iterative Voting Improves Social Welfare
Recent work in iterative voting has defined the additive dynamic price of
anarchy (ADPoA) as the difference in social welfare between the truthful and
worst-case equilibrium profiles resulting from repeated strategic
manipulations. While iterative plurality has been shown to only return
alternatives with at most one less initial votes than the truthful winner, it
is less understood how agents' welfare changes in equilibrium. To this end, we
differentiate agents' utility from their manipulation mechanism and determine
iterative plurality's ADPoA in the worst- and average-cases. We first prove
that the worst-case ADPoA is linear in the number of agents. To overcome this
negative result, we study the average-case ADPoA and prove that equilibrium
winners have a constant order welfare advantage over the truthful winner in
expectation. Our positive results illustrate the prospect for social welfare to
increase due to strategic manipulation.Comment: 21 pages, 5 figures, in NeurIPS 202
Scanner Invariant Representations for Diffusion MRI Harmonization
Purpose: In the present work we describe the correction of diffusion-weighted
MRI for site and scanner biases using a novel method based on invariant
representation.
Theory and Methods: Pooled imaging data from multiple sources are subject to
variation between the sources. Correcting for these biases has become very
important as imaging studies increase in size and multi-site cases become more
common. We propose learning an intermediate representation invariant to
site/protocol variables, a technique adapted from information theory-based
algorithmic fairness; by leveraging the data processing inequality, such a
representation can then be used to create an image reconstruction that is
uninformative of its original source, yet still faithful to underlying
structures. To implement this, we use a deep learning method based on
variational auto-encoders (VAE) to construct scanner invariant encodings of the
imaging data.
Results: To evaluate our method, we use training data from the 2018 MICCAI
Computational Diffusion MRI (CDMRI) Challenge Harmonization dataset. Our
proposed method shows improvements on independent test data relative to a
recently published baseline method on each subtask, mapping data from three
different scanning contexts to and from one separate target scanning context.
Conclusion: As imaging studies continue to grow, the use of pooled multi-site
imaging will similarly increase. Invariant representation presents a strong
candidate for the harmonization of these data
Optimized Realization of Bayesian Networks in Reduced Normal Form using Latent Variable Model
Bayesian networks in their Factor Graph Reduced Normal Form (FGrn) are a
powerful paradigm for implementing inference graphs. Unfortunately, the
computational and memory costs of these networks may be considerable, even for
relatively small networks, and this is one of the main reasons why these
structures have often been underused in practice. In this work, through a
detailed algorithmic and structural analysis, various solutions for cost
reduction are proposed. An online version of the classic batch learning
algorithm is also analyzed, showing very similar results (in an unsupervised
context); which is essential even if multilevel structures are to be built. The
solutions proposed, together with the possible online learning algorithm, are
included in a C++ library that is quite efficient, especially if compared to
the direct use of the well-known sum-product and Maximum Likelihood (ML)
algorithms. The results are discussed with particular reference to a Latent
Variable Model (LVM) structure.Comment: 20 pages, 8 figure
Providing a foundation for interpretable autonomous agents through elicitation and modeling of criminal investigation pathways
Criminal investigations are guided by repetitive and time-consuming information retrieval tasks, often with high risk and high consequence. If Artificial intelligence (AI) systems can automate lines of inquiry, it could reduce the burden on analysts and allow them to focus their efforts on analysis. However, there is a critical need for algorithmic transparency to address ethical concerns. In this paper, we use data gathered from Cognitive Task Analysis (CTA) interviews of criminal intelligence analysts and perform a novel analysis method to elicit question networks. We show how these networks form an event tree, where events are consolidated by capturing analyst intentions. The event tree is simplified with a Dynamic Chain Event Graph (DCEG) that provides a foundation for transparent autonomous investigations
Consistent Range Approximation for Fair Predictive Modeling
This paper proposes a novel framework for certifying the fairness of
predictive models trained on biased data. It draws from query answering for
incomplete and inconsistent databases to formulate the problem of consistent
range approximation (CRA) of fairness queries for a predictive model on a
target population. The framework employs background knowledge of the data
collection process and biased data, working with or without limited statistics
about the target population, to compute a range of answers for fairness
queries. Using CRA, the framework builds predictive models that are certifiably
fair on the target population, regardless of the availability of external data
during training. The framework's efficacy is demonstrated through evaluations
on real data, showing substantial improvement over existing state-of-the-art
methods
Gene Expression and its Discontents: Developmental disorders as dysfunctions of epigenetic cognition
Systems biology presently suffers the same mereological and sufficiency fallacies that haunt neural network models of high order cognition. Shifting perspective from the massively parallel space of gene matrix interactions to the grammar/syntax of the time series of expressed phenotypes using a cognitive paradigm permits import of techniques from statistical physics via the homology between information source uncertainty and free energy density. This produces a broad spectrum of possible statistical models of development and its pathologies in which epigenetic regulation and the effects of embedding environment are analogous to a tunable enzyme catalyst. A cognitive paradigm naturally incorporates memory, leading directly to models of epigenetic inheritance, as affected by environmental exposures, in the largest sense. Understanding gene expression, development, and their dysfunctions will require data analysis tools considerably more sophisticated than the present crop of simplistic models abducted from neural network studies or stochastic chemical reaction theory
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