Europe
Solving QBF Instances with Nested SAT Solvers
Bogaerts, Bart (KU Leuven) | Janhunen, Tomi (Aalto University) | Tasharrofi, Shahab (Aalto University)
Recent work by Janhunen, Tasharrofi, and Ternovska (2016) started from the following observation: "if SAT From the result of this oracle call, a learned clause is generated and added to ϕ. Now that formalism; (2) It can be immediately combined with other these highly-performant SATsolvers exist, research often SAT extensions (such as integer variables, acyclicity, or any stretches beyond SAT, either because of trying to tackle other theory propagator); (3) No dedicated propagators need problems of a complexity higher than NP or because the input to be developed for the new extension because the nested format of SAT solvers (propositional logic) is too limited solver is (automatically) used as a propagator for its internal to concisely and naturally express certain domain specific theory; for example, it was shown by Janhunen, Tasharrofi, constraints, such as graph properties.
Subset Minimization in Dynamic Programming on Tree Decompositions
Bliem, Bernhard (TU Wien) | Charwat, Günther (TU Wien) | Hecher, Markus (TU Wien) | Woltran, Stefan (TU Wien)
Many problems from the area of AI have been shown tractable for bounded treewidth. In order to put such results into practice, quite involved dynamic programming (DP) algorithms on tree decompositions have to be designed and implemented. These algorithms typically show recurring patterns that call for tasks like subset minimization. In this paper, we provide a new method for obtaining DP algorithms from simpler principles, where the necessary data structures and algorithms for subset minimization are automatically generated. Moreover, we discuss how this method can be implemented in systems that perform more space-efficiently than current approaches.
Extension Variables in QBF Resolution
Beyersdorf, Olaf (University of Leeds) | Chew, Leroy (University of Leeds) | Janota, Mikolas (Microsoft Research, Cambridge)
We investigate two QBF resolution systems that use extension variables: weak extended Q-resolution, where the extension variables are quantified at the innermost level, and extended Q-resolution, where the extension variables can be placed inside the quantifier prefix. These systems have been considered previously by Wintersteiger et al, who give experimental evidence that extended Q-resolution is stronger than weak extended Q-resolution. Here we prove an exponential separation between the two systems, thereby confirming the conjecture of Wintersteiger et al. Conceptually, this separation relies on showing strategy extraction for weak extended Q-resolution by bounded-depth circuits. In contrast, we show that this strong strategy extraction result fails in extended Q-resolution.
Clauses Versus Gates in CEGAR-Based 2QBF Solving
Balabanov, Valeriy (Mentor Graphics) | Jiang, Jie-Hong Roland (National Taiwan University) | Mishchenko, Alan (University of California, Berkeley) | Scholl, Christoph (University of Freiburg)
2QBF is a special case of general quantified Boolean formulae (QBF). It is limited to just two quantification levels, i.e., to a form forall-exists. Despite this limitation it applies to a wide range of applications, e.g., to artificial intelligence, graph theory, synthesis, etc.. Recent research showed that CEGAR-based methods give a performance boost to QBF solving (e.g, compared to QDPLL). Conjunctive normal form (CNF) is a commonly accepted representation for both SAT and QBF problems; however, it does not reflect the circuit structure that might be present in the problem. Existing attempts of extracting this structure from CNF and using it in 2QBF context do not show advantages over CNF based 2QBF solvers. In this work we introduce a new workflow for 2QBF, containing a new semantic circuit extraction algorithm and a CEGAR-based 2QBF solver that uses circuit structure and is improved by a so-called "cofactor sharing'' heuristics. We evaluate the proposed methodology on a range of benchmarks and show the practicality of the new approach.
Planning under Uncertainty for Aggregated Electric Vehicle Charging Using Markov Decision Processes
Walraven, Erwin (Delft University of Technology) | Spaan, Matthijs T. J. (Delft University of Technology)
The increasing penetration of renewable energy sources and electric vehicles raises important challenges related to the operation of electricity grids. For instance, the amount of power generated by wind turbines is time-varying and dependent on the weather, which makes it hard to match flexible electric vehicle demand and uncertain wind power supply. In this paper we propose a vehicle aggregation framework which uses Markov Decision Processes to control charging of multiple electric vehicles and deals with uncertainty in renewable supply. We present a grouping technique to address the scalability aspects of our framework. In experiments we show that the aggregation framework maximizes the profit of the aggregator while reducing usage of conventionally-generated power and cost of customers.
An MDP-Based Winning Approach to Autonomous Power Trading: Formalization and Empirical Analysis
Urieli, Daniel (The University of Texas at Austin) | Stone, Peter (The University of Texas at Austin)
With the efforts of moving to sustainable and reliable energy supply, electricity markets are undergoing far-reaching changes. Due to the high-cost of failure in the real-world, it is important to test new market structures in simulation. This is the focus of the Power Trading Agent Competition (Power TAC), which proposes autonomous electricity broker agents as a means for stabilizing the electricity grid. This paper focuses on the question: how should an autonomous electricity broker agent act in competitive electricity markets to maximize its profit. We formalize the complete electricity trading problem as a continuous, high-dimensional Markov Decision Process (MDP), which is computationally intractable to solve. Our formalization provides a guideline for approximating the MDP's solution, and for extending existing solutions. We show that a previously champion broker can be viewed as approximating the solution using a lookahead policy. We present TacTex15, which improves upon this previous approximation and achieves state-of-the-art performance in competitions and controlled experiments. Using thousands of experiments against 2015 finalist brokers, we analyze TacTex15's performance and the reasons for its success. We find that lookahead policies can be effective, but their performance can be sensitive to errors in the transition function prediction, specifically demand-prediction.
Proactive Dynamic DCOPs
Hoang, Khoi (New Mexico State University) | Fioretto, Ferdinando ( New Mexico State University ) | Hou, Ping ( New Mexico State University ) | Yokoo, Makoto ( Kyushu University ) | Yeoh, William ( New Mexico State University ) | Zivan, Roie ( Ben-Gurion University )
The current approaches to model dynamism in DCOPs solve a sequence of static problems, reacting to the changes in the environment as the agents observe them. Such approaches, thus, ignore possible predictions on the environment evolution. To overcome such limitations, we introduce the Proactive Dynamic DCOP (PD-DCOP) model, a novel formalism to model dynamic DCOPs in the presence of exogenous uncertainty. In contrast to reactive approaches, PD-DCOPs are able to explicitly model the possible changes to the problem, and take such information into account proactively, when solving the dynamically changing problem.
Bayesian Networks with Prior Knowledge for Malware Phylogenetics
Oyen, Diane (Los Alamos National Laboratory) | Anderson, Blake (Cisco Systems, Inc) | Anderson-Cook, Christine (Los Alamos National Laboratory)
Malware phylogenetics help cybersecurity experts to quickly understand a new malware sample by placing the new sample in the context of similar samples that have been previously reverse engineered. Recently, researchers have begun using malware code as data to infer directed acyclic graphs (DAG) that model the evolutionary relationships among samples of malware. A DAG is the ideal model for a phylogenetic graph because it includes the merges and branches that are often present in malware evolution. We present a novel Bayesian network discovery algorithm for learning a DAG via statistical inference of conditional dependencies from observed data with an informative prior on the partial ordering of variables. Our approach leverages the information on edge direction that a human can provide and the edge presence inference which data can provide. We give an efficient implementation of the partial-order prior in a Bayesian structure discovery learning algorithm, as well as a related structure prior, showing that both priors meet the local modularity requirement necessary for the efficient Bayesian discovery algorithm. We apply our algorithm to learn phylogenetic graphs on three malicious families and two benign families where the ground truth is known; and show that compared to competing algorithms, our algorithm more accurately identifies directed edges.
Taxonomy of Pathways to Dangerous Artificial Intelligence
Yampolskiy, Roman V. (University of Louisville)
In order to properly handle a dangerous Artificially Intelligent (AI) system it is important to understand how the system came to be in such a state. In popular culture (science fiction movies/books) AIs/Robots became self-aware and as a result rebel against humanity and decide to destroy it. While it is one possible scenario, it is probably the least likely path to appearance of dangerous AI. In this work, we survey, classify and analyze a number of circumstances, which might lead to arrival of malicious AI. To the best of our knowledge, this is the first attempt to systematically classify types of pathways leading to malevolent AI. Previous relevant work either surveyed specific goals/meta-rules which might lead to malevolent behavior in AIs (Özkural 2014) or reviewed specific undesirable behaviors AGIs can exhibit at different stages of its development (Turchin July 10 2015a, Turchin July 10, 2015b).
Using Stories to Teach Human Values to Artificial Agents
Riedl, Mark O. (Georgia Institute of Technology) | Harrison, Brent (Georgia Institute of Technology)
Value alignment is a property of an intelligent agent indicating that it can only pursue goals that are beneficial to humans. Successful value alignment should ensure that an artificial general intelligence cannot intentionally or unintentionally perform behaviors that adversely affect humans. This is problematic in practice since it is difficult to exhaustively enumerated by human programmers. In order for successful value alignment, we argue that values should be learned. In this paper, we hypothesize that an artificial intelligence that can read and understand stories can learn the values tacitly held by the culture from which the stories originate.We describe preliminary work on using stories to generate a value-aligned reward signal for reinforcement learning agents that prevents psychotic-appearing behavior.