30,226 research outputs found
Recursive Online Enumeration of All Minimal Unsatisfiable Subsets
In various areas of computer science, we deal with a set of constraints to be
satisfied. If the constraints cannot be satisfied simultaneously, it is
desirable to identify the core problems among them. Such cores are called
minimal unsatisfiable subsets (MUSes). The more MUSes are identified, the more
information about the conflicts among the constraints is obtained. However, a
full enumeration of all MUSes is in general intractable due to the large number
(even exponential) of possible conflicts. Moreover, to identify MUSes
algorithms must test sets of constraints for their simultaneous satisfiabilty.
The type of the test depends on the application domains. The complexity of
tests can be extremely high especially for domains like temporal logics, model
checking, or SMT. In this paper, we propose a recursive algorithm that
identifies MUSes in an online manner (i.e., one by one) and can be terminated
at any time. The key feature of our algorithm is that it minimizes the number
of satisfiability tests and thus speeds up the computation. The algorithm is
applicable to an arbitrary constraint domain and its effectiveness demonstrates
itself especially in domains with expensive satisfiability checks. We benchmark
our algorithm against state of the art algorithm on Boolean and SMT constraint
domains and demonstrate that our algorithm really requires less satisfiability
tests and consequently finds more MUSes in given time limits
Steric constraints in model proteins
A simple lattice model for proteins that allows for distinct sizes of the
amino acids is presented. The model is found to lead to a significant number of
conformations that are the unique ground state of one or more sequences or
encodable. Furthermore, several of the encodable structures are highly
designable and are the non-degenerate ground state of several sequences. Even
though the native state conformations are typically compact, not all compact
conformations are encodable. The incorporation of the hydrophobic and polar
nature of amino acids further enhances the attractive features of the model.Comment: RevTex, 5 pages, 3 postscript figure
Exhaustive enumeration unveils clustering and freezing in random 3-SAT
We study geometrical properties of the complete set of solutions of the
random 3-satisfiability problem. We show that even for moderate system sizes
the number of clusters corresponds surprisingly well with the theoretic
asymptotic prediction. We locate the freezing transition in the space of
solutions which has been conjectured to be relevant in explaining the onset of
computational hardness in random constraint satisfaction problems.Comment: 4 pages, 3 figure
Intelligent Energy Optimization for User Intelligible Goals in Smart Home Environments
Intelligent management of energy consumption is one of the key issues for future energy distribution systems, smart buildings, and consumer appliances. The problem can be tackled both from the point of view of the utility provider, with the intelligence embedded in the smart grid, or from the point of view of the consumer, thanks to suitable local energy management systems (EMS). Conserving energy, however, should respect the user requirements regarding the desired state of the environment, therefore an EMS should constantly and intelligently find the balance between user requirements and energy saving. The paper proposes a solution to this problem, based on explicit high-level modeling of user intentions and automatic control of device states through the solution and optimization of a constrained Boolean satisfiability problem. The proposed approach has been integrated into a smart environment framework, and promising preliminary results are reporte
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