4,762 research outputs found
Formal Verification of Nonlinear Inequalities with Taylor Interval Approximations
We present a formal tool for verification of multivariate nonlinear
inequalities. Our verification method is based on interval arithmetic with
Taylor approximations. Our tool is implemented in the HOL Light proof assistant
and it is capable to verify multivariate nonlinear polynomial and
non-polynomial inequalities on rectangular domains. One of the main features of
our work is an efficient implementation of the verification procedure which can
prove non-trivial high-dimensional inequalities in several seconds. We
developed the verification tool as a part of the Flyspeck project (a formal
proof of the Kepler conjecture). The Flyspeck project includes about 1000
nonlinear inequalities. We successfully tested our method on more than 100
Flyspeck inequalities and estimated that the formal verification procedure is
about 3000 times slower than an informal verification method implemented in
C++. We also describe future work and prospective optimizations for our method.Comment: 15 page
Grafting Hypersequents onto Nested Sequents
We introduce a new Gentzen-style framework of grafted hypersequents that
combines the formalism of nested sequents with that of hypersequents. To
illustrate the potential of the framework, we present novel calculi for the
modal logics and , as well as for extensions of the
modal logics and with the axiom for shift
reflexivity. The latter of these extensions is also known as
in the context of deontic logic. All our calculi enjoy syntactic cut
elimination and can be used in backwards proof search procedures of optimal
complexity. The tableaufication of the calculi for and
yields simplified prefixed tableau calculi for these logic
reminiscent of the simplified tableau system for , which might be
of independent interest
On Counterexample Guided Quantifier Instantiation for Synthesis in CVC4
We introduce the first program synthesis engine implemented inside an SMT
solver. We present an approach that extracts solution functions from
unsatisfiability proofs of the negated form of synthesis conjectures. We also
discuss novel counterexample-guided techniques for quantifier instantiation
that we use to make finding such proofs practically feasible. A particularly
important class of specifications are single-invocation properties, for which
we present a dedicated algorithm. To support syntax restrictions on generated
solutions, our approach can transform a solution found without restrictions
into the desired syntactic form. As an alternative, we show how to use
evaluation function axioms to embed syntactic restrictions into constraints
over algebraic datatypes, and then use an algebraic datatype decision procedure
to drive synthesis. Our experimental evaluation on syntax-guided synthesis
benchmarks shows that our implementation in the CVC4 SMT solver is competitive
with state-of-the-art tools for synthesis
Proof Simplification in the Framework of Coherent Logic
The problem of proof simplification draws a lot of attention to itself across various contexts. In this paper, we present one approach for simplifying proofs constructed in the framework of coherent logic. This approach is motivated by the need for filtering-out "clean'' and short proofs from proof-traces, which typically contain many irrelevant steps, and which are generated by automated theorem provers - in this case, theorem provers based on coherent logic. Such "clean'' proofs can then be used for producing readable proofs in natural-language form. The proof simplification procedure consists of three transformation steps. The first one is based on the elimination of inference steps which are irrelevant for the present proof, also allowing some irrelevant branchings to be eliminated, the second one consists of lifting-up steps through the branching steps, followed by elimination of repeated steps, while the third one serves to convert proof fragments into the reductio ad absurdum form, if possible. In contrast to general simplification procedures, our proof simplification procedure is specific for a fragment of first order logic and therefore simple and easy to implement, and allows simple generation of object level proofs. We proceed to prove that this procedure is correct and terminating, and also that it never increases the size of a proof. Finally, we implement the proof simplification procedure, and provide several example proofs
Linearization of CIF Through SOS
Linearization is the procedure of rewriting a process term into a linear
form, which consist only of basic operators of the process language. This
procedure is interesting both from a theoretical and a practical point of view.
In particular, a linearization algorithm is needed for the Compositional
Interchange Format (CIF), an automaton based modeling language.
The problem of devising efficient linearization algorithms is not trivial,
and has been already addressed in literature. However, the linearization
algorithms obtained are the result of an inventive process, and the proof of
correctness comes as an afterthought. Furthermore, the semantic specification
of the language does not play an important role on the design of the algorithm.
In this work we present a method for obtaining an efficient linearization
algorithm, through a step-wise refinement of the SOS rules of CIF. As a result,
we show how the semantic specification of the language can guide the
implementation of such a procedure, yielding a simple proof of correctness.Comment: In Proceedings EXPRESS 2011, arXiv:1108.407
A Survey of Satisfiability Modulo Theory
Satisfiability modulo theory (SMT) consists in testing the satisfiability of
first-order formulas over linear integer or real arithmetic, or other theories.
In this survey, we explain the combination of propositional satisfiability and
decision procedures for conjunctions known as DPLL(T), and the alternative
"natural domain" approaches. We also cover quantifiers, Craig interpolants,
polynomial arithmetic, and how SMT solvers are used in automated software
analysis.Comment: Computer Algebra in Scientific Computing, Sep 2016, Bucharest,
Romania. 201
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