257,637 research outputs found
Constraint Expressions and Workflow Satisfiability
A workflow specification defines a set of steps and the order in which those
steps must be executed. Security requirements and business rules may impose
constraints on which users are permitted to perform those steps. A workflow
specification is said to be satisfiable if there exists an assignment of
authorized users to workflow steps that satisfies all the constraints. An
algorithm for determining whether such an assignment exists is important, both
as a static analysis tool for workflow specifications, and for the construction
of run-time reference monitors for workflow management systems. We develop new
methods for determining workflow satisfiability based on the concept of
constraint expressions, which were introduced recently by Khan and Fong. These
methods are surprising versatile, enabling us to develop algorithms for, and
determine the complexity of, a number of different problems related to workflow
satisfiability.Comment: arXiv admin note: text overlap with arXiv:1205.0852; to appear in
Proceedings of SACMAT 201
Performance of the online track reconstruction and impact on hadronic triggers at the CMS High Level Trigger
The trigger systems of the LHC detectors play a crucial role in determining
the physics capabilities of the experiments. A reduction of several orders of
magnitude of the event rate is needed to reach values compatible with the
detector readout, offline storage and analysis capabilities. The CMS experiment
has been designed with a two-level trigger system: the Level 1 (L1) Trigger,
implemented on custom-designed electronics, and the High Level Trigger (HLT), a
streamlined version of the CMS reconstruction and analysis software running on
a computer farm. The software-base HLT requires a trade-off between the
complexity of the algorithms, the sustainable output rate, and the selection
efficiency. This is going to be even more challenging during Run II, with a
higher centre-of-mass energy, a higher instantaneous luminosity and pileup, and
the impact of out-of-time pileup due to the 25 ns bunch spacing. The online
algorithms need to be optimised for such a complex environment in order to keep
the output rate under control without impacting the physics efficiency of the
online selection. Tracking, for instance, will play an even more important role
in the event reconstruction. In this poster we will present the performance of
the online track and vertex reconstruction algorithms, and their impact on the
hadronic triggers that make use of b-tagging and of jets reconstructed with the
Particle Flow technique. We will show the impact of these triggers on physics
performance of the experiment, and the latest plans for improvements in view of
the Run II data taking in 2015.Comment: arXiv admin note: substantial text overlap with arXiv:1403.150
Discovering Petri Net Models of Discrete-Event Processes by Computing T-Invariants
International audienceThis paper addresses the problem of discovering a Petri Net (PN) from a long event sequence representing the behavior of discrete-event processes. A method for building a 1-bounded PN able to execute the events sequence S is presented; it is based on determining causality and concurrence relations between events and computing the t-invariants. This novel method determines the structure and the initial marking of an ordinary PN, which reproduces the behavior in S. The algorithms derived from the method are efficient and have been implemented and tested on numerous examples of diverse complexity. Note to PractitionersâModel discovery is useful to perform reverse engineering of ill-known systems. The algorithms proposed in this paper build 1-bounded PN models, which are enough powerful to describe many discrete-event processes from industry. The efficiency of the method allows processing very large sequences. Thus, an automated modeling tool can be developed for dealing with data issued from real systems
Efficient algorithms for reconfiguration in VLSI/WSI arrays
The issue of developing efficient algorithms for reconfiguring processor arrays in the presence of faulty processors and fixed hardware resources is discussed. The models discussed consist of a set of identical processors embedded in a flexible interconnection structure that is configured in the form of a rectangular grid. An array grid model based on single-track switches is considered. An efficient polynomial time algorithm is proposed for determining feasible reconfigurations for an array with a given distribution of faulty processors. In the process, it is shown that the set of conditions in the reconfigurability theorem is not necessary. A polynomial time algorithm is developed for finding feasible reconfigurations in an augmented single-track model and in array grid models with multiple-track switche
Algorithms in algebraic number theory
In this paper we discuss the basic problems of algorithmic algebraic number
theory. The emphasis is on aspects that are of interest from a purely
mathematical point of view, and practical issues are largely disregarded. We
describe what has been done and, more importantly, what remains to be done in
the area. We hope to show that the study of algorithms not only increases our
understanding of algebraic number fields but also stimulates our curiosity
about them. The discussion is concentrated of three topics: the determination
of Galois groups, the determination of the ring of integers of an algebraic
number field, and the computation of the group of units and the class group of
that ring of integers.Comment: 34 page
On the calculation of the linear complexity of periodic sequences
Based on a result of Hao Chen in 2006 we present a general procedure how to reduce the determination of the linear complexity of a sequence over a finite field \F_q of period to the determination of the linear complexities of sequences over \F_q of period . We apply this procedure to some classes of
periodic sequences over a finite field \F_q obtaining efficient algorithms to determine the linear complexity
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