2,524 research outputs found
The communication processor of TUMULT-64
Tumult (Twente University MULTi-processor system) is a modular extendible multi-processor system designed and implemented at the Twente University of Technology in co-operation with Oce Nederland B.V. and the Dr. Neher Laboratories (Dutch PTT). Characteristics of the hardware are: MIMD type, distributed memory, message passing, high performance, real-time and fault tolerant. A distributed real-time operating system has been realized, consisting of a multi-tasking kernel per node, inter process communication via typed messages and a distributed file system. In this paper first a brief description of the system is given, after that the architecture of the communication processor will be discussed. Reduction of the communication overhead due to message passing will be emphasized.\ud
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Throughput of Streaming Applications Running on a Multiprocessor Architecture
We study the timing behaviour of streaming applications running on a multiprocessor architecture. Dependencies are derived between the application throughput and the timing characteristics of the processors and communication. Four different processor organizations that strongly influenced the results are considered and compared
Efficient Inter-Task Communication for Nested Loop Programs on a Multiprocessor System
In modern multiprocessor systems, processors can be stalled by inter-task communication when reading from a remote buffer. This paper presents a solution for the inter-task communication, that has a minimal impact on the performance of the system, hides the inter-task communication latency without requiring additional hardware. The solution applies to jobs, represented as task graphs, where the tasks are nested loop programs. Buffers are allocated in scratch-pad memories of the consuming tasks to provide low latency read access. For the nested loop programs, minimal buffer sizes can be determined to cover all possible communication patterns. The added computational complexity is low, as the solution adds only a few operations to the nested loop programs
Modeling the Temperature Bias of Power Consumption for Nanometer-Scale CPUs in Application Processors
We introduce and experimentally validate a new macro-level model of the CPU
temperature/power relationship within nanometer-scale application processors or
system-on-chips. By adopting a holistic view, this model is able to take into
account many of the physical effects that occur within such systems. Together
with two algorithms described in the paper, our results can be used, for
instance by engineers designing power or thermal management units, to cancel
the temperature-induced bias on power measurements. This will help them gather
temperature-neutral power data while running multiple instance of their
benchmarks. Also power requirements and system failure rates can be decreased
by controlling the CPU's thermal behavior.
Even though it is usually assumed that the temperature/power relationship is
exponentially related, there is however a lack of publicly available physical
temperature/power measurements to back up this assumption, something our paper
corrects. Via measurements on two pertinent platforms sporting nanometer-scale
application processors, we show that the power/temperature relationship is
indeed very likely exponential over a 20{\deg}C to 85{\deg}C temperature range.
Our data suggest that, for application processors operating between 20{\deg}C
and 50{\deg}C, a quadratic model is still accurate and a linear approximation
is acceptable.Comment: Submitted to SAMOS 2014; International Conference on Embedded
Computer Systems: Architectures, Modeling, and Simulation (SAMOS XIV
Interacting Agents and Continuous Opinions Dynamics
We present a model of opinion dynamics in which agents adjust continuous
opinions as a result of random binary encounters whenever their difference in
opinion is below a given threshold. High thresholds yield convergence of
opinions towards an average opinion, whereas low thresholds result in several
opinion clusters. The model is further generalised to network interactions,
threshold heterogeneity, adaptive thresholds and binary strings of opinions.Comment: 21 pages, 13 figures.
http://www.lps.ens.fr/~weisbuch/contopidyn/contopidyn.htm
Self-coherent camera as a focal plane wavefront sensor: simulations
Direct detection of exoplanets requires high dynamic range imaging.
Coronagraphs could be the solution, but their performance in space is limited
by wavefront errors (manufacturing errors on optics, temperature variations,
etc.), which create quasi-static stellar speckles in the final image. Several
solutions have been suggested for tackling this speckle noise. Differential
imaging techniques substract a reference image to the coronagraphic residue in
a post-processing imaging. Other techniques attempt to actively correct
wavefront errors using a deformable mirror. In that case, wavefront aberrations
have to be measured in the science image to extremely high accuracy. We propose
the self-coherent camera sequentially used as a focal-plane wavefront sensor
for active correction and differential imaging. For both uses, stellar speckles
are spatially encoded in the science image so that differential aberrations are
strongly minimized. The encoding is based on the principle of light incoherence
between the hosting star and its environment. In this paper, we first discuss
one intrinsic limitation of deformable mirrors. Then, several parameters of the
self-coherent camera are studied in detail. We also propose an easy and robust
design to associate the self-coherent camera with a coronagraph that uses a
Lyot stop. Finally, we discuss the case of the association with a four-quadrant
phase mask and numerically demonstrate that such a device enables the detection
of Earth-like planets under realistic conditions. The parametric study of the
technique lets us believe it can be implemented quite easily in future
instruments dedicated to direct imaging of exoplanets.Comment: 15 pages, 14 figures, accepted in A&A (here is the final version
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