9,086 research outputs found
A comprehensive approach in performance evaluation for modernreal-time operating systems
In real-time computing the accurate characterization of the performance and determinism that a particular real-time operating system/hardware combination can provide for real-time applications is essential. This issue is not properly addressed by existing performance metrics mainly due to the lack of completeness and generalization. In this paper we present a set of comprehensive, easy-to-implement and useful metrics covering three basic real-time operating system features: response to external events, intertask synchronization and resource sharing, and intertask data transferring. The evaluation of real-time operating systems using a set of fine-grained metrics is fundamental to guarantee that we can reach the required determinism in real-world applications.Publicad
Trains, Games, and Complexity: 0/1/2-Player Motion Planning through Input/Output Gadgets
We analyze the computational complexity of motion planning through local
"input/output" gadgets with separate entrances and exits, and a subset of
allowed traversals from entrances to exits, each of which changes the state of
the gadget and thereby the allowed traversals. We study such gadgets in the 0-,
1-, and 2-player settings, in particular extending past
motion-planning-through-gadgets work to 0-player games for the first time, by
considering "branchless" connections between gadgets that route every gadget's
exit to a unique gadget's entrance. Our complexity results include containment
in L, NL, P, NP, and PSPACE; as well as hardness for NL, P, NP, and PSPACE. We
apply these results to show PSPACE-completeness for certain mechanics in
Factorio, [the Sequence], and a restricted version of Trainyard, improving
prior results. This work strengthens prior results on switching graphs and
reachability switching games.Comment: 37 pages, 36 figure
Exploiting AWG Free Spectral Range Periodicity in Distributed Multicast Architectures
Modular optical switch architectures combining wavelength routing based on
arrayed waveguide grating (AWG) devices and multicasting based on star couplers
hold promise for flexibly addressing the exponentially growing traffic demands
in a cost- and power-efficient fashion. In a default switching scenario, an
input port of the AWG is connected to an output port via a single wavelength.
This can severely limit the capacity between broadcast domains, resulting in
interdomain traffic switching bottlenecks. In this paper, we examine the
possibility of resolving capacity bottlenecks by exploiting multiple AWG free
spectral ranges (FSRs), i.e., setting up multiple parallel connections between
each pair of broadcast domains. To this end, we introduce a multi-FSR
scheduling algorithm for interconnecting broadcast domains by fairly
distributing the wavelength resources among them. We develop a general-purpose
analytical framework to study the blocking probabilities in a multistage
switching scenario and compare our results with Monte Carlo simulations. Our
study points to significant improvements with a moderate increase in the number
of FSRs. We show that an FSR count beyond four results in diminishing returns.
Furthermore, to investigate the trade-offs between the network- and
physical-layer effects, we conduct a cross-layer analysis, taking into account
pulse amplitude modulation (PAM) and rate-adaptive forward error correction
(FEC). We illustrate how the effective bit rate per port increases with an
increase in the number of FSRs. %We also look at the advantages of an
impairment-aware scheduling strategy in a multi-FSR switching scenario
SICStus MT - A Multithreaded Execution Environment for SICStus Prolog
The development of intelligent software agents and other
complex applications which continuously interact with their
environments has been one of the reasons why explicit concurrency has
become a necessity in a modern Prolog system today. Such applications
need to perform several tasks which may be very different with respect
to how they are implemented in Prolog. Performing these tasks
simultaneously is very tedious without language support.
This paper describes the design, implementation and evaluation of a
prototype multithreaded execution environment for SICStus Prolog. The
threads are dynamically managed using a small and compact set of
Prolog primitives implemented in a portable way, requiring almost no
support from the underlying operating system
Expanded delta networks for very large parallel computers
In this paper we analyze a generalization of the traditional delta network, introduced by Patel [21], and dubbed Expanded Delta Network (EDN). These networks provide in general multiple paths that can be exploited to reduce contention in the network resulting in increased performance. The crossbar and traditional delta networks are limiting cases of this class of networks. However, the delta network does not provide the multiple paths that the more general expanded delta networks provide, and crossbars are to costly to use for large networks. The EDNs are analyzed with respect to their routing capabilities in the MIMD and SIMD models of computation.The concepts of capacity and clustering are also addressed. In massively parallel SIMD computers, it is the trend to put a larger number processors on a chip, but due to I/O constraints only a subset of the total number of processors may have access to the network. This is introduced as a Restricted Access Expanded Delta Network of which the MasPar MP-1 router network is an example
Towards Useful Overall Network Teletraffic Definitions
A detailed conceptual and a corresponding analytical traffic models of an overall (virtual) circuit
switching telecommunication system are used. The models are relatively close to real-life communication
systems with homogeneous terminals. In addition to Normalized and Pie-Models Ensue Model and Denial Traffic
concept are proposed, as a parts of a technique for presentation and analysis of overall network traffic models
functional structure; The ITU-T definitions for: fully routed, successful and effective attempts, and effective traffic
are re-formulated. Definitions for fully routed traffic and successful traffic are proposed, because they are absent
in the ITU-T recommendations; A definition of demand traffic (absent in ITU-T Recommendations) is proposed.
For each definition are appointed: 1) the correspondent part of the conceptual model graphical presentation; 2)
analytical equations, valid for mean values, in a stationary state. This allows real network traffic considered to be
classified more precisely and shortly. The proposed definitions are applicable for every telecommunication
system
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