Real-time management of complex resource allocation systems: Necessity, achievements and further challenges

Abstract

Many contemporary applications, ranging from flexibly automated production systems, to automated material handling and intelligent transportation systems, to internet-based workflow management systems, and more recently, to the massively parallelized software systems that emerge in the context of the novel multi-core computing architectures, can be perceived as a set of finite resources that support a number of concurrently running processes. These processes execute in a staged manner and, at each stage, they vie for the allocation of various subsets of the system resources. To effectively support and manage the extensive levels of concurrency and operational flexibility that are contemplated for these environments, and the ensuing complexity, there is a substantial need for formal models and tools that will enable the modeling, analysis and eventually the control of the aforementioned resource allocation function so that the resulting dynamics are, both, behaviorally correct and operationally efficient. This article overviews a research program that seeks to address the aforementioned need by using the unifying abstraction of the resource allocation system (RAS) and supporting modeling frameworks, like automata, Petri nets, and Markov reward and decision processes, borrowed from the area of Discrete Event Systems (DES) theory. The presented results take advantage of the special structure that exists in the considered RAS classes, and they are characterized by their analytical rigor and computational tractability. The article also highlights the further challenges that must be addressed for the successful completion and promotion of the pursued framework.

Robust deadlock avoidance for sequential resource allocation systems with resource outages

“…Research Background and Motivation: The problem of deadlock avoidance in sequential resource allocation systems (RAS) is well documented and extensively studied in the literature [1], [2]. In its basic positioning, the problem concerns the staged allocation of a limited set of reusable resources to a set of concurrently executing processes in a way that all of these processes can secure the resources necessary for the execution of their various processing stages and terminate successfully.…”

“…Nevertheless, recent developments taking place in the Ph.D. theses of [8], [9] and their derivative publications 1 have established that the deployment of the maximally permissive DAP is still a tractable proposition for RAS instances of pretty high structural and behavioral complexity, through a two-step approach that isolates the hardest part of the computation of this policy in an "offline" computational stage, and eventually encodes the obtained results as a "classifier" that dichotomizes the underlying RAS state set into its admissible and inadmissible subsets. 2 Finally, instrumental in all the aforementioned developments, is the classification of the various RAS structures according to the taxonomy that is presented in Table I. As seen in Table I, this taxonomy is defined on the basis of the structure of (i) the [6] Based on the Process Based on the Sequential Logic Requirement Vectors Linear: Each process is Single-Unit: Each stage defined by a linear sequence requires a single unit of stages from a single resource Disjunctive: A number of Single-Type: Each stage alternative process plans requires an arbitrary encoded by an acyclic number of units, but all digraph from a single resource Merge-Split: Each process Conjunctive: Stages reis a fork-join network quire different resources Complex: A combination at arbitrary levels of the above behaviors sequential logic that is observed by the RAS processes, and (ii) the resource requests that are posed by the various processing stages.…”

“…Among those publications, some of the most relevant to this work are those presented in[10],[11],[12]; see also[13] for an abridged exposition of all the corresponding results 2. In the relevant terminology, the RAS subset that contains the admissible (resp., inadmissible) states by the maximally permissive DAP is also known as the "safe" (resp., "unsafe") subset.…”