arXiv subjects

Olga Tveretina

Publications and source records attributed to Olga Tveretina.

8 recordsLinked to original sources

arXiv2017

ParaPlan: A Tool for Parallel Reachability Analysis of Planar Polygonal Differential Inclusion Systems

We present the ParaPlan tool which provides the reachability analysis of planar hybrid systems defined by differential inclusions (SPDI). It uses the parallelized and optimized version of the algorithm underlying the SPeeDI tool. The performance comparison demonstrates the speed-up of up to 83 times with respect to the sequential implementation on various benchmarks. Some of the benchmarks we used are randomly generated with the novel approach based on the partitioning of the plane with Voronoi diagrams.

cs.DC↗

arXiv2017

Resolution Simulates Ordered Binary Decision Diagrams for Formulas in Conjunctive Normal Form

A classical question of propositional logic is one of the shortest proof of a tautology. A related fundamental problem is to determine the relative efficiency of standard proof systems, where the relative complexity is measured using the notion of polynomial simulation. Presently, the state-of-the-art satisfiability algorithms are based on resolution in combination with search. An Ordered Binary Decision Diagram (OBDD) is a data structure that is used to represent Boolean functions. Groote and Zantema have proved that there is exponential separation between resolution and a proof system based on limited OBDD derivations. However, formal comparison of these methods is not straightforward because OBDDs work on arbitrary formulas, whereas resolution can only be applied to formulas in Conjunctive Normal Form (CNFs). Contrary to popular belief, we argue that resolution simulates OBDDs polynomially if we limit both to CNFs and thus answer negatively the open question of Groote and Zantema whether there exist unsatisfiable CNFs having polynomial OBDD refutations and requiring exponentially long resolution refutations.

cs.LO↗

arXiv2016

Configuring Cloud-Service Interfaces Using Flow Inheritance

Technologies for composition of loosely-coupled web services in a modular and flexible way are in high demand today. On the one hand, the services must be flexible enough to be reused in a variety of contexts. On the other hand, they must be specific enough so that their composition may be provably consistent. The existing technologies (WS-CDL, WSCI and session types) require a behavioural contract associated with each service, which is impossible to derive automatically. Furthermore, neither technology supports flow inheritance: a mechanism that automatically and transparently propagates data through service pipelines. This paper presents a novel mechanism for automatic interface configuration of such services. Instead of checking consistency of the behavioural contracts, our approach focuses solely on that of data formats in the presence of subtyping, polymorphism and flow inheritance. The paper presents a toolchain that automatically derives service interfaces from the code and performs interface configuration taking non-local constraints into account. Although the configuration mechanism is global, the services are compiled separately. As a result, the mechanism does not raise source security issues despite global service availability in adaptable form.

cs.SE↗

arXiv2016

A Constraint Satisfaction Method for Configuring Non-Local Service Interfaces

Modularity and decontextualisation are core principles of a service-oriented architecture. However, the principles are often lost when it comes to an implementation of services, as a result of a rigidly defined service interface. The interface, which defines a data format, is typically specific to a particular context and its change entails significant redevelopment costs. This paper focuses on a two-fold problem. On the one hand, the interface description language must be flexible enough for maintaining service compatibility in a variety of different contexts without modification of the service itself. On the other hand, the composition of interfaces in a distributed environment must be provably consistent. The existing approaches for checking compatibility of service choreographies are either inflexible (WS-CDL and WSCI) or require behaviour specification associated with each service, which is often impossible to provide in practice. We present a novel approach for automatic interface configuration in distributed stream-connected components operating as closed-source services (i.e. the behavioural protocol is unknown). We introduce a Message Definition Language (MDL), which can extend the existing interfaces description languages, such as WSDL, with support of subtyping, inheritance and polymorphism. The MDL supports configuration variables that link input and output interfaces of a service and propagate requirements over an application graph. We present an algorithm that solves the interface reconciliation problem using constraint satisfaction that relies on Boolean satisfiability as a subproblem.

cs.LO↗

arXiv2015

Interface Reconciliation in Kahn Process Networks using CSP and SAT

We present a new CSP- and SAT-based approach for coordinating interfaces of distributed stream-connected components provided as closed-source services. The Kahn Process Network (KPN) is taken as a formal model of computation and a Message Definition Language (MDL) is introduced to describe the format of messages communicated between the processes. MDL links input and output interfaces of a node to support flow inheritance and contextualisation. Since interfaces can also be linked by the existence of a data channel between them, the match is generally not only partial but also substantially nonlocal. The KPN communication graph thus becomes a graph of interlocked constraints to be satisfied by specific instances of the variables. We present an algorithm that solves the CSP by iterative approximation while generating an adjunct Boolean SAT problem on the way. We developed a solver in OCaml as well as tools that analyse the source code of KPN vertices to derive MDL terms and automatically modify the code by propagating type definitions back to the vertices after the CSP has been solved. Techniques and approaches are illustrated on a KPN implementing an image processing algorithm as a running example.

cs.PL↗

arXiv2014

A Case Study in Coordination Programming: Performance Evaluation of S-Net vs Intel's Concurrent Collections

We present a programming methodology and runtime performance case study comparing the declarative data flow coordination language S-Net with Intel's Concurrent Collections (CnC). As a coordination language S-Net achieves a near-complete separation of concerns between sequential software components implemented in a separate algorithmic language and their parallel orchestration in an asynchronous data flow streaming network. We investigate the merits of S-Net and CnC with the help of a relevant and non-trivial linear algebra problem: tiled Cholesky decomposition. We describe two alternative S-Net implementations of tiled Cholesky factorization and compare them with two CnC implementations, one with explicit performance tuning and one without, that have previously been used to illustrate Intel CnC. Our experiments on a 48-core machine demonstrate that S-Net manages to outperform CnC on this problem.

cs.PL↗

arXiv2011

Deciding Reachability for 3-Dimensional Multi-Linear Systems

This paper deals with the problem of point-to-point reachability in multi-linear systems. These systems consist of a partition of the Euclidean space into a finite number of regions and a constant derivative assigned to each region in the partition, which governs the dynamical behavior of the system within it. The reachability problem for multi-linear systems has been proven to be decidable for the two-dimensional case and undecidable for the dimension three and higher. Multi-linear systems however exhibit certain properties that make them very suitable for topological analysis. We prove that reachability can be decided exactly in the 3-dimensional case when systems satisfy certain conditions. We show with experiments that our approach can be orders of magnitude more efficient than simulation.

cs.LO↗

arXiv2009

An Exponential Lower Bound on OBDD Refutations for Pigeonhole Formulas

Haken proved that every resolution refutation of the pigeonhole formula has at least exponential size. Groote and Zantema proved that a particular OBDD computation of the pigeonhole formula has an exponential size. Here we show that any arbitrary OBDD refutation of the pigeonhole formula has an exponential size, too: we prove that the size of one of the intermediate OBDDs is at least $Ω(1.025^n)$.

cs.CC↗