15,246 research outputs found
Reachability Analysis of Communicating Pushdown Systems
The reachability analysis of recursive programs that communicate
asynchronously over reliable FIFO channels calls for restrictions to ensure
decidability. Our first result characterizes communication topologies with a
decidable reachability problem restricted to eager runs (i.e., runs where
messages are either received immediately after being sent, or never received).
The problem is EXPTIME-complete in the decidable case. The second result is a
doubly exponential time algorithm for bounded context analysis in this setting,
together with a matching lower bound. Both results extend and improve previous
work from La Torre et al
Automatic Verification of Erlang-Style Concurrency
This paper presents an approach to verify safety properties of Erlang-style,
higher-order concurrent programs automatically. Inspired by Core Erlang, we
introduce Lambda-Actor, a prototypical functional language with
pattern-matching algebraic data types, augmented with process creation and
asynchronous message-passing primitives. We formalise an abstract model of
Lambda-Actor programs called Actor Communicating System (ACS) which has a
natural interpretation as a vector addition system, for which some verification
problems are decidable. We give a parametric abstract interpretation framework
for Lambda-Actor and use it to build a polytime computable, flow-based,
abstract semantics of Lambda-Actor programs, which we then use to bootstrap the
ACS construction, thus deriving a more accurate abstract model of the input
program. We have constructed Soter, a tool implementation of the verification
method, thereby obtaining the first fully-automatic, infinite-state model
checker for a core fragment of Erlang. We find that in practice our abstraction
technique is accurate enough to verify an interesting range of safety
properties. Though the ACS coverability problem is Expspace-complete, Soter can
analyse these verification problems surprisingly efficiently.Comment: 12 pages plus appendix, 4 figures, 1 table. The tool is available at
http://mjolnir.cs.ox.ac.uk/soter
TRACTABLE DATA-FLOW ANALYSIS FOR DISTRIBUTED SYSTEMS
Automated behavior analysis is a valuable technique in the development and maintainence of distributed systems. In this paper, we present a tractable dataflow analysis technique for the detection of unreachable states and actions in distributed systems. The technique follows an approximate approach described by Reif and Smolka, but delivers a more accurate result in assessing unreachable states and actions. The higher accuracy is achieved by the use of two concepts: action dependency and history sets. Although the technique, does not exhaustively detect all possible errors, it detects nontrivial errors with a worst-case complexity quadratic to the system size. It can be automated and applied to systems with arbitrary loops and nondeterministic structures. The technique thus provides practical and tractable behavior analysis for preliminary designs of distributed systems. This makes it an ideal candidate for an interactive checker in software development tools. The technique is illustrated with case studies of a pump control system and an erroneous distributed program. Results from a prototype implementation are presented
A Polynomial Translation of pi-calculus FCPs to Safe Petri Nets
We develop a polynomial translation from finite control pi-calculus processes
to safe low-level Petri nets. To our knowledge, this is the first such
translation. It is natural in that there is a close correspondence between the
control flows, enjoys a bisimulation result, and is suitable for practical
model checking.Comment: To appear in special issue on best papers of CONCUR'12 of Logical
Methods in Computer Scienc
Prioritized Random MAC Optimization via Graph-based Analysis
Motivated by the analogy between successive interference cancellation and
iterative belief-propagation on erasure channels, irregular repetition slotted
ALOHA (IRSA) strategies have received a lot of attention in the design of
medium access control protocols. The IRSA schemes have been mostly analyzed for
theoretical scenarios for homogenous sources, where they are shown to
substantially improve the system performance compared to classical slotted
ALOHA protocols. In this work, we consider generic systems where sources in
different importance classes compete for a common channel. We propose a new
prioritized IRSA algorithm and derive the probability to correctly resolve
collisions for data from each source class. We then make use of our theoretical
analysis to formulate a new optimization problem for selecting the transmission
strategies of heterogenous sources. We optimize both the replication
probability per class and the source rate per class, in such a way that the
overall system utility is maximized. We then propose a heuristic-based
algorithm for the selection of the transmission strategy, which is built on
intrinsic characteristics of the iterative decoding methods adopted for
recovering from collisions. Experimental results validate the accuracy of the
theoretical study and show the gain of well-chosen prioritized transmission
strategies for transmission of data from heterogenous classes over shared
wireless channels
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