74 research outputs found
BigraphER: rewriting and analysis engine for bigraphs
BigraphER is a suite of open-source tools providing an effi-
cient implementation of rewriting, simulation, and visualisation for bigraphs,
a universal formalism for modelling interacting systems that
evolve in time and space and first introduced by Milner. BigraphER consists
of an OCaml library that provides programming interfaces for the
manipulation of bigraphs, their constituents and reaction rules, and a
command-line tool capable of simulating Bigraphical Reactive Systems
(BRSs) and computing their transition systems. Other features are native
support for both bigraphs and bigraphs with sharing, stochastic reaction
rules, rule priorities, instantiation maps, parameterised controls, predicate
checking, graphical output and integration with the probabilistic
model checker PRISM
Effective problem solving using SAT solvers
In this article we demonstrate how to solve a variety of problems and puzzles
using the built-in SAT solver of the computer algebra system Maple. Once the
problems have been encoded into Boolean logic, solutions can be found (or shown
to not exist) automatically, without the need to implement any search
algorithm. In particular, we describe how to solve the -queens problem, how
to generate and solve Sudoku puzzles, how to solve logic puzzles like the
Einstein riddle, how to solve the 15-puzzle, how to solve the maximum clique
problem, and finding Graeco-Latin squares.Comment: To appear in Proceedings of the Maple Conference 201
Solving and Verifying the Boolean Pythagorean Triples Problem via Cube-and-Conquer
We solved a long-outstanding open problem in Ramsey theory, using SAT solving
Encoding Redundancy for Satisfaction-Driven Clause Learning
Satisfaction-Driven Clause Learning (SDCL) is a recent SAT
solving paradigm that aggressively trims the search space of possible truth assignments. To determine if the SAT solver is currently exploring a dispensable part of the search space, SDCL uses the so-called positive reduct of a formula: The positive reduct is an easily solvable propositional formula that is satisfiable if the current assignment of the solver can be safely pruned from the search space. In this paper, we present two novel variants of the positive reduct that allow for even more aggressive pruning. Using one of these variants allows SDCL to solve harder problems, in particular the well-known Tseitin formulas and mutilated chessboard problems. For the first time, we are able to generate and automatically check clausal proofs for large instances of these problems
Lower estimate of the number of steps for an inverting normal algorithm and other similar algorithms
Evolutionary algorithms for the satisfiability problem
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