2,450 research outputs found
Modeling and Verification of Dynamic Command Scheduling for Real-Time Memory Controllers
In modern multi-core systems with multiple real-time (RT) applications, memory traffic accessing the shared SDRAM is increasingly diverse, e.g., transactions have variable sizes. RT memory controllers with dynamic command scheduling can efficiently address the diversity by issuing appropriate commands subject to the SDRAM timing constraints. However, the scheduling dependencies between commands make it challenging to derive tight bounds for the worst-case response time (WCRT) and the worst-case bandwidth (WCBW) of a memory controller. Existing modeling and analysis techniques either do not provide tight WCRT and WCBW bounds for diverse memory traffic with variable transaction sizes or are difficult to adapt to different RT memory controllers. This paper models a memory controller using Timed Automata (TA), where model checking is applied for analysis. Our TA model is modular and accurately captures the behavior of a RT memory controller with dynamic command scheduling. We obtain WCRT and WCBW bounds, which are validated by simulating the worst- case transaction traces obtained by model checking with a cycle-accurate model of the memory controller. Our method outperforms three state-of-the-art analysis techniques. We reduce WCRT bound by up to 20%, while the average improvement is 7.7%, and increase the WCBW bound by up to 25% with an average improvement of 13.6%. In addition, our modeling is generic enough to extend to memory controllers with different mechanisms
Single - particle correlations in events with the total disintegration of nuclei
New experimental data on the behaviour of the single-particle two-dimensional
correlation functions R versus Q (Q is the number of nucleons emitted from nuc-
lei) and Ap (Ap is the mass of projectile nuclei) are presented in this paper.
The interactions of protons, d, 4He and 12C nuclei with carbon nuclei (at a
momentum of 4.2 A GeV/c) are considered.The values of R are obtained separately
for pi minus mesons and protons.In so doing,the values of R are normalized so
that -1=<R=<1.The value of R=0 corresponds to the case of the absence of corre-
lations.It has been found that the Q- and Ap-dependence of R takes place only
for weak correlations (R< 0.3).In the main (90 %),these correlations are con-
nected with the variable pt and have a nonlinear character, that is the regi-
ons with different characters of the Q-dependence of R are separated: there is
a change of regimes in the Q-dependences of R.The correlations weaken with
increasing Ap, and the variable R gets the least values of all the considered
ones in 12CC interactions.Simultaneously with weakening the correlations in the
region of large Q, the character of the Q-dependence of R changes.Comment: 17 pages, submitted to Phys. Rew.
Multiple Interactions in Two-Photon Collisions
We compute cross sections for events where two pairs of partons scatter off
each other in the same reaction, giving rise to at least 3
high--{\mbox{}} jets. Unlike in {\mbox{}}\ collisions we find
the signal to lie well above the background from higher order QCD processes. If
the usual ``eikonaliztion" assumption is correct, the signal should be readily
observable at LEP2, and might already be detectable in data taken at TRISTAN.Comment: 8 pages, plain LaTeX, 2 figures (not included). A compressed PS file
of the entire paper, including figures, can be obtained via anonymous ftp
from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-921.ps.
Production in Au+Au and pp Collisions at = 200GeV at STAR
Mid-rapidity and are
measured in Au+Au and pp collisions at =200GeV using the STAR
detector at RHIC. The mass is systematically shifted at small
transverse momentum for both Au+Au and pp collisions. The
transverse mass spectra are measured in Au+Au collisions at different
centralities and in pp collisions. The mean transverse momentum
as a function of the collision centrality is compared to those of identified
, and . The and ratios are
compared to measurements in A+A, , , collisions at
various colliding energies. The physics implications of these measurements are
also discussed.Comment: 6 pages, 4 figures, proceedings of Strange Quarks in Matter
(SQM2003), Atlantic Beach, USA, to be published in J. Phys.
Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
We discuss three different cases of hard inclusive spectra in proton-proton
collisions: high single hadron production at 20 GeV and
at = 62.4 GeV, and direct photon production at = 200 GeV;
with regard to their relevance for the search of Quark Gluon Plasma signals in
A+A collisions at SPS and RHIC energies.Comment: Proceeds. Hot Quarks 2004 Int. Workshop on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions. 26 pages. 26 figs. [minor
corrs., refs. added
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A Globally Arbitrated Memory Tree for Mixed-Time-Criticality Systems
Embedded systems are increasingly based on multi-core platforms to accommodate a growing number of applications, some of which have real-time requirements. Resources, such as off-chip DRAM, are typically shared between the applications using memory interconnects with different arbitration polices to cater to diverse bandwidth and latency requirements. However, traditional centralized interconnects are not scalable as the number of clients increase. Similarly, current distributed interconnects either cannot satisfy the diverse requirements or have decoupled arbitration stages, resulting in larger area, power and worst-case latency. The four main contributions of this article are: 1) a Globally Arbitrated Memory Tree (GAMT) with a distributed architecture that scales well with the number of cores, 2) an RTL-level implementation that can be configured with five arbitration policies (three distinct and two as special cases), 3) the concept of mixed arbitration policies that allows the policy to be selected individually per core, and 4) a worst-case analysis for a mixed arbitration policy that combines TDM and FBSP arbitration.We compare the performance of GAMT with centralized implementations and show that it can run up to four times faster and have over 51 and 37 percent reduction in area and power consumption, respectively, for a given bandwidth
Studying minijets via the dependence of two-particle correlation in azimuthal angle
Following my previous proposal that two-particle correlation functions can be
used to resolve the minijet contribution to particle production in minimum
biased events of high energy hadronic interactions, I study the and
energy dependence of the correlation. Using HIJING Monte Carlo model, it is
found that the correlation in azimuthal angle between
two particles with resembles much like two back-to-back jets as
increases at high colliding energies due to minijet production. It
is shown that , which is related to the relative fraction of
particles from minijets, increases with energy. The background of the
correlation for fixed also grows with energy due to the increase of
multiple minijet production. Application of this analysis to the study of jet
quenching in ultrarelativistic heavy ion collisions is also discussed.Comment: 11 pages Latex text and 8 ps figures, LBL-3349
Communicating Processes with Data for Supervisory Coordination
We employ supervisory controllers to safely coordinate high-level
discrete(-event) behavior of distributed components of complex systems.
Supervisory controllers observe discrete-event system behavior, make a decision
on allowed activities, and communicate the control signals to the involved
parties. Models of the supervisory controllers can be automatically synthesized
based on formal models of the system components and a formalization of the safe
coordination (control) requirements. Based on the obtained models, code
generation can be used to implement the supervisory controllers in software, on
a PLC, or an embedded (micro)processor. In this article, we develop a process
theory with data that supports a model-based systems engineering framework for
supervisory coordination. We employ communication to distinguish between the
different flows of information, i.e., observation and supervision, whereas we
employ data to specify the coordination requirements more compactly, and to
increase the expressivity of the framework. To illustrate the framework, we
remodel an industrial case study involving coordination of maintenance
procedures of a printing process of a high-tech Oce printer.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432
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