The Experts below are selected from a list of 69 Experts worldwide ranked by ideXlab platform
Angelo Montanari - One of the best experts on this subject based on the ideXlab platform.
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Computational Intelligence, Volume 12. Number 3. 1996 EFFICIENT TEMPORAL REASONING IN THE Cached EVENT CALCULUS
2016Co-Authors: L. Chiitaro, Angelo MontanariAbstract:This article deals with the problem of providing Kowalski and Sergot’s event calculus. extended with context dependency, with an efficient implementation in a logic programming framework. Despite a widespread recognition that a positive solution to efficiency issues is necessary to guarantee the computational feasibility of existing approaches to temporal reasoning, the problem of analyzing the complexity of temporal reasoning programs has been largely overlooked. This article provides a mathematical analysis of the efficiency of query and update processing in the event calculus and defines a Cached Version of the calculus that (i) moves computational complexity from query to update processing and (ii) features an absolute improvement of performance. because query processing in the event calculus costs much more than update processing in the proposed Cached Version. Key words: event calculus, temporal reasoning complexity, database query and update, caching. 1
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EFFICIENT TEMPORAL REASONING IN THE Cached EVENT CALCULUS
Computational Intelligence, 1996Co-Authors: Luca Chittaro, Angelo MontanariAbstract:This article deals with the problem of providing Kowaiski and Sergot's event calculus, extended with context dependency, with an efficient implementation in a logic programming framework. Despite a widespread recognition that a positive solution to efficiency issues is necessary to guarantee the computational feasibility of existing approaches to temporal reasoning, the problem of analyzing the complexity of temporal reasoning programs has been largely overlooked. This article provides a mathematical analysis of the efficiency of query and update processing in the event calculus and defines a Cached Version of the calculus that (i) moves computational complexity from query to update processing and (ii) features an absolute improvement of performance, because query processing in the event calculus costs much more than update processing in the proposed Cached Version.
Luca Chittaro - One of the best experts on this subject based on the ideXlab platform.
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EFFICIENT TEMPORAL REASONING IN THE Cached EVENT CALCULUS
Computational Intelligence, 1996Co-Authors: Luca Chittaro, Angelo MontanariAbstract:This article deals with the problem of providing Kowaiski and Sergot's event calculus, extended with context dependency, with an efficient implementation in a logic programming framework. Despite a widespread recognition that a positive solution to efficiency issues is necessary to guarantee the computational feasibility of existing approaches to temporal reasoning, the problem of analyzing the complexity of temporal reasoning programs has been largely overlooked. This article provides a mathematical analysis of the efficiency of query and update processing in the event calculus and defines a Cached Version of the calculus that (i) moves computational complexity from query to update processing and (ii) features an absolute improvement of performance, because query processing in the event calculus costs much more than update processing in the proposed Cached Version.
Andy Wellings - One of the best experts on this subject based on the ideXlab platform.
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RTS - Adding instruction cache effect to an exact schedulability analysis of preemptive real-time systems
Proceedings of the Eighth Euromicro Workshop on Real-Time Systems, 1Co-Authors: J.v. Busquets-mataix, J.j. Serrano-martin, R. Ors-carot, Pedro Gil, Andy WellingsAbstract:Cache memories are commonly avoided in real-time systems because of their unpredictable behavior. Recently, some research has been done to obtain tighter bounds on the worst case execution time (WCET) of Cached programs. These techniques usually assume a non preemptive underlying system. However, some techniques can be applied to allow the use of caches in preemptive systems. This paper describes how to incorporate the effect of instruction cache to the Response Time schedulability Analysis (RTA). RTA is an efficient analysis for preemptive fixed priority schedulers. We also compare through simulations the results of such an approach to the previously available CRMA (Cached RMA: cache effect is incorporated in the utilization based Rate Monotonic schedulability analysis). The results show that the Cached Version of RTA (CRTA) clearly outperforms CRMA.
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IEEE Real Time Technology and Applications Symposium - Adding instruction cache effect to schedulability analysis of preemptive real-time systems
Proceedings Real-Time Technology and Applications, 1Co-Authors: J.v. Busquets-mataix, Pedro Gil, Juan José Serrano, Rafael Ors, Andy WellingsAbstract:Cache memories are commonly avoided in real time systems because of their unpredictable behavior. Recently, some research has been done to obtain tighter bounds on the worst case execution time (WCET) of Cached programs. These techniques usually assume a non preemptive underlying system. However, some techniques can be applied to allow the use of caches in preemptive systems. The paper describes how to incorporate the effect of instruction cache to the Response Time schedulability Analysis (RTA). RTA is an efficient analysis for preemptive fixed priority schedulers. We also compare through simulations the results of such an approach to both cache partitioning (increase of the cache predictability by assigning private cache partitions to tasks) and CRMA (Cached RMA: cache effect is incorporated in the utilization based rate monotonic schedulability analysis). The results show that the Cached Version of RTA (CRTA) clearly outperforms CRMA, however the partitioning scheme may be better depending on the system configuration. The obtained results bound the applicability domain for each method for a variety of hardware and workload configurations. The results can be used as design guidelines.
J.v. Busquets-mataix - One of the best experts on this subject based on the ideXlab platform.
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RTS - Adding instruction cache effect to an exact schedulability analysis of preemptive real-time systems
Proceedings of the Eighth Euromicro Workshop on Real-Time Systems, 1Co-Authors: J.v. Busquets-mataix, J.j. Serrano-martin, R. Ors-carot, Pedro Gil, Andy WellingsAbstract:Cache memories are commonly avoided in real-time systems because of their unpredictable behavior. Recently, some research has been done to obtain tighter bounds on the worst case execution time (WCET) of Cached programs. These techniques usually assume a non preemptive underlying system. However, some techniques can be applied to allow the use of caches in preemptive systems. This paper describes how to incorporate the effect of instruction cache to the Response Time schedulability Analysis (RTA). RTA is an efficient analysis for preemptive fixed priority schedulers. We also compare through simulations the results of such an approach to the previously available CRMA (Cached RMA: cache effect is incorporated in the utilization based Rate Monotonic schedulability analysis). The results show that the Cached Version of RTA (CRTA) clearly outperforms CRMA.
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IEEE Real Time Technology and Applications Symposium - Adding instruction cache effect to schedulability analysis of preemptive real-time systems
Proceedings Real-Time Technology and Applications, 1Co-Authors: J.v. Busquets-mataix, Pedro Gil, Juan José Serrano, Rafael Ors, Andy WellingsAbstract:Cache memories are commonly avoided in real time systems because of their unpredictable behavior. Recently, some research has been done to obtain tighter bounds on the worst case execution time (WCET) of Cached programs. These techniques usually assume a non preemptive underlying system. However, some techniques can be applied to allow the use of caches in preemptive systems. The paper describes how to incorporate the effect of instruction cache to the Response Time schedulability Analysis (RTA). RTA is an efficient analysis for preemptive fixed priority schedulers. We also compare through simulations the results of such an approach to both cache partitioning (increase of the cache predictability by assigning private cache partitions to tasks) and CRMA (Cached RMA: cache effect is incorporated in the utilization based rate monotonic schedulability analysis). The results show that the Cached Version of RTA (CRTA) clearly outperforms CRMA, however the partitioning scheme may be better depending on the system configuration. The obtained results bound the applicability domain for each method for a variety of hardware and workload configurations. The results can be used as design guidelines.
Pascal Felber - One of the best experts on this subject based on the ideXlab platform.
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Evaluating the Price of Consistency in Distributed File Storage Services
2013Co-Authors: José Valerio, Pierre Sutra, Etienne Rivière, Pascal FelberAbstract:Distributed file storage services (DFSS) such as Dropbox, iCloud, SkyDrive, or Google Drive, offer a filesystem interface to a distributed data store. DFSS usually differ in the consistency level they provide for concurrent accesses: a client might access a Cached Version of a file, see the immediate results of all prior operations, or temporarily observe an inconsistent state. The selection of a consistency level has a strong impact on performance. It is the result of an inherent tradeoff between three properties: consistency, availability, and partition-tolerance. Isolating and identifying the exact impact on performance is a difficult task, because DFSS are complex designs with multiple components and dependencies. Furthermore, each system has a different range of features, its own design and implementation, and various optimizations that do not allow for a fair comparison. In this paper, we make a step towards a principled comparison of DFSS components, focusing on the evaluation of consistency mechanisms. We propose a novel modular DFSS testbed named FlexiFS, which implements a range of state-of-the-art techniques for the distribution, replication, routing, and indexing of data. Using FlexiFS, we survey six consistency levels: linearizability, sequential consistency, and eventual consistency, each operating with and without close-to-open semantics. Our evaluation shows that: (i) as expected, POSIX semantics (i.e., linearizability without close-to-open semantics) harm performance; and (ii) when close-to-open semantics is in use, linearizability delivers performance similar to sequential or eventual consistency.
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DAIS - Evaluating the Price of Consistency in Distributed File Storage Services
Distributed Applications and Interoperable Systems, 2013Co-Authors: José Valerio, Pierre Sutra, Etienne Rivière, Pascal FelberAbstract:Distributed file storage services (DFSS) such as Dropbox, iCloud, SkyDrive, or Google Drive, offer a filesystem interface to a distributed data store. DFSS usually differ in the consistency level they provide for concurrent accesses: a client might access a Cached Version of a file, see the immediate results of all prior operations, or temporarily observe an inconsistent state. The selection of a consistency level has a strong impact on performance. It is the result of an inherent tradeoff between three properties: consistency, availability, and partition-tolerance. Isolating and identifying the exact impact on performance is a difficult task, because DFSS are complex designs with multiple components and dependencies. Furthermore, each system has a different range of features, its own design and implementation, and various optimizations that do not allow for a fair comparison. In this paper, we make a step towards a principled comparison of DFSS components, focusing on the evaluation of consistency mechanisms. We propose a novel modular DFSS testbed named FlexiFS, which implements a range of state-of-the-art techniques for the distribution, replication, routing, and indexing of data. Using FlexiFS, we survey six consistency levels: linearizability, sequential consistency, and eventual consistency, each operating with and without close-to-open semantics. Our evaluation shows that: (i) as expected, POSIX semantics (i.e., linearizability without close-to-open semantics) harm performance; and (ii) when close-to-open semantics is in use, linearizability delivers performance similar to sequential or eventual consistency.
