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Resolving classical concurrency problems using outlier detection

Smoliński M.

Journal of Applied Computer Science

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2017

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Vol. 25, nr 2

69--88

EN

In this paper outlier detection is used to determine anomaly between tasks to prevent occurrence of resource conflicts in prepared schedule. Determined conflictless schedule bases on controlling access of tasks to groups of shared resources. Proposed approach allows to prepare conflictless schedule of effcient parallel task processing without resource conflicts and is dedicated to environments of task processing with high contention of shared resources. In this paper the outlier detection is used to resolve two classical concurrency problems: readers and writers and dining philosophers. In opposition to other known solutions of concurrency problems, proposed approach can be applied to solve different problems and do not require to use additional mechanisms of task synchronization. The universality of proposed approach allows to prepare conflictless schedule even in environments, where classical concurrency problems will be significantly expanded and complicated.

2

The GPU performance in coordination of parallel tasks in access to resource groups without conflicts

Smoliński M.

Information Systems in Management

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2017

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Vol. 6, No. 2

143--153

EN

In high contention environments, with limited number of shared resources, elimination of resource conflicts between tasks processed in parallel is required. Execution of all tasks without resource conflicts can be achieved by preparing a proper overall schedule for all of them. The effective calculation of conflict-free execution plan for tasks provides the conflictless scheduling algorithm that is dedicated to GPU massively parallel processing. The conflictless scheduling algorithm base on rapid resource conflict detection to mutual exclusion of conflicted tasks in access to global resources and is an alternative to other task synchronization methods. This article presents the performance of modern GPU in calculations of adaptive conflictless task schedule. The performance analysis also takes into account all data transfers to and from the GPU memory in various phases of the conflictless task scheduling algorithm.

3

Elimination of task starvation in conflictless scheduling concept

Smoliński M.

Information Systems in Management

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2016

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Vol. 5, No. 2

237--247

EN

New concept of conflictless task scheduling is an alternative approach to existing solutions in concurrency. Conflictless task scheduling includes data structures and algorithm that prevents occurrence of resource conflict between tasks executed in parallel. The range of applications the conflictless task scheduling includes different environments like transactions processing in database management systems, scheduling of processes or threads in operating systems or business processes management. Task scheduling without any resource conflicts is dedicated to high contention of limited resources environments and its algorithm can be implemented in modern GPU. This paper presents concept of local task scheduling without resources conflicts occurrence, discusses features of new approach and focuses on problem of task starvation. Elimination of task starvation is included in conflictless task scheduling concept, detailed explanation are contained in this paper.

4

Deadlock freeness supervisor for marked graph

Sioud H., Achour Z., Sava A., Rezg N.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2009

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Vol. 57, nr 3

281-289

EN

This note presents a control synthesis approach for discrete event systems modeled by marked graphs with uncontrollable transitions. The forbidden behavior is specified by General Mutual Exclusion Constraints (GMEC). We prove that, even if the system to be controlled .s live, the closed loop control may generate deadlock situations. Using the structural proprieties of marked graph we defined the causes of deadlock situations, and we defined a formal method to avoid them.

5

Fuzziness and constraints programming for AGVs system control

Bocewicz G., Bach I., Banaszak Z.

Systems Science

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2007

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Vol. 33, no 1

27-38

EN

The subject matter of the study is a deadlock-free supervisory control for the automated guided vehicles (AGV) that operate in a common workspace of a flexible manufacturing system (FMS). An AGV provides load/unload services to some workstations while moving along a cyclic transportation route. So, since transport and service operations are repetitive, hence the transport processes considered are modeled as a system of cyclic concurrent processes sharing common traveling intervals with mutual exclusion. The processes execution has to guarantee the collision-free and deadlock free AGVs flow. In this paper the problem of determination of the rules coordinating access of the vehicles to the shared travel route intervals, ensuring the collision-free and deadlock-free execution of the repetitive processes was reduced to determination of the sufficient conditions assumed be a pair (an initial state, a set of dispatching rules). In particular the problem of searching for a pair is defined in the form of the constraint satisfaction problem (CSP) and is solved with use of the logic programming techniques. Proposed approach provides the framework allowing one to take into account both: distinct (pointed), and imprecise (fuzzy) data, in a unified way and treated in a unified form of discrete CSP. The approach considered regards of the logic-algebraic method based and CP-driven methodology aimed at interactive decision making based on distinct and imprecise data. The illustrative examples are provided.