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1.
The Pipelining Communications Middleware (PCM) approach provides a flexible, simple, high-performance mechanism to connect parallel programs running on high performance
computers or clusters. This approach enables parallel programs to communicate and coordinate with each other to address larger
problems than a single program can solve. The motivation behind the PCM approach grew out of using files as an intermediate
transfer stage between processing by different programs. Our approach supersedes this practice by using streaming data set
transfers as an “online” communication channel between simultaneously active parallel programs. Thus, the PCM approach addresses
the issue of sending data from a parallel program to another parallel program without exposing details such as number of nodes
allocated to the program, specific node identifiers, etc. This paper outlines and analyzes our proposed computation and communication
model to provide efficient and convenient communications between parallel programs running on high performance computing systems
or clusters. We also discuss the PCM challenges as well as current PCM implementations. Our approach achieves scalability,
transparency, coordination, synchronization and flow control, and efficient programming. We experimented with data parallel
applications to evaluate the performance of the PCM approach. Our experiment results show that the PCM approach achieves nearly
ideal throughput that scales linearly with the underlying network medium speed. PCM performs well with small and large data
transfers. Furthermore, our experiments show that network infrastructure plays the most significant role in the PCM performance.
相似文献
Stephen JenksEmail: |
2.
The performance of synchronous parallel polynomial root extraction on a ring multicomputer 总被引:1,自引:0,他引:1
Hamid Sarbazi-Azad 《Cluster computing》2007,10(2):167-174
In this paper, a parallel algorithm for computing the roots of a given polynomial of degree n on a ring of processors is proposed.
The algorithm implements Durand–Kerner’s method and consists of two phases: initialisation, and iteration. In the initialisation
phase all the necessary preparation steps are realised to start the parallel computation. It includes register initialisation
and initial approximation of roots requiring 3n−2 communications, 2 exponentiation, one multiplications, 6 divisions, and 4n−3 additions. In the iteration phase, these initial approximated roots are corrected repeatedly and converge to their accurate
values. The iteration phase is composed of some iteration steps, each consisting of 3n communications, 4n+3 additions, 3n+1 multiplications, and one division.
相似文献
Hamid Sarbazi-AzadEmail: Email: |
3.
Advances in virtualization technology have focused mainly on strengthening the isolation barrier between virtual machines
(VMs) that are co-resident within a single physical machine. At the same time, a large category of communication intensive
distributed applications and software components exist, such as web services, high performance grid applications, transaction
processing, and graphics rendering, that often wish to communicate across this isolation barrier with other endpoints on co-resident
VMs. State of the art inter-VM communication mechanisms do not adequately address the requirements of such applications. TCP/UDP
based network communication tends to perform poorly when used between co-resident VMs, but has the advantage of being transparent
to user applications. Other solutions exploit inter-domain shared memory mechanisms to improve communication latency and bandwidth,
but require applications or user libraries to be rewritten against customized APIs—something not practical for a large majority
of distributed applications. In this paper, we present the design and implementation of a fully transparent and high performance
inter-VM network loopback channel, called XenLoop, in the Xen virtual machine environment. XenLoop does not sacrifice user-level
transparency and yet achieves high communication performance between co-resident guest VMs. XenLoop intercepts outgoing network
packets beneath the network layer and shepherds the packets destined to co-resident VMs through a high-speed inter-VM shared
memory channel that bypasses the virtualized network interface. Guest VMs using XenLoop can migrate transparently across machines
without disrupting ongoing network communications, and seamlessly switch between the standard network path and the XenLoop
channel. In our evaluation using a number of unmodified benchmarks, we observe that XenLoop can reduce the inter-VM round
trip latency by up to a factor of 5 and increase bandwidth by a up to a factor of 6.
相似文献
Kartik Gopalan (Corresponding author)Email: |
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Large-scale scientific computing applications frequently make use of closely-coupled distributed parallel components. The
performance of such applications is therefore dependent on the component parts and their interaction at run-time. This paper
describes a methodology for predictive performance modelling and evaluation of parallel applications composed of multiple
interacting components. In this paper, the fundamental steps and required operations involved in the modelling and evaluation
process are identified—including component decomposition, component model combination, M×N communication modelling, dataflow analysis and overall performance evaluation. A case study is presented to illustrate the
modelling process and the methodology is verified through experimental analysis.
相似文献
Stephen A. JarvisEmail: |
7.
Philip Richard Sullivan 《Biology & philosophy》2009,24(1):65-79
This paper demonstrates that the human visual system, the primary sensory conduit for primates, processes ambient energy in
a way that obligatorily constructs the objects that we ineluctably perceive. And since our perceptual apparatus processes
information only in terms of objects (along with the properties and movements of objects), we are limited in our ability to comprehend ‘what
is’ when we move beyond our ordinary world of midsize objects—as, for example, when we address the micro microworld of quantum
physics.
相似文献
Philip Richard SullivanEmail: |
8.
Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
9.
This paper introduces a threshold policy with hysteresis (TPH) for the control of one-predator one-prey models. The models studied are the Lotka–Volterra and Rosenzweig–MacArthur
two species density-dependent predator–prey models and the Arditi–Ginzburg nondimensional ratio-dependent model. The proposed
policy (TPH) changes the dynamics of the system in such a way that a bounded oscillation is achieved confined to a region
that does not allow extinction of either species. The policy can be designed by a suitable choice of so called virtual equilibrium
points in a simple and intuitive manner.
相似文献
Amit Bhaya (Corresponding author)Email: |
10.
Luis Emilio Bruni 《Biosemiotics》2008,1(1):113-130
This article considers categorical perception (CP) as a crucial process involved in all sort of communication throughout the
biological hierarchy, i.e. in all of biosemiosis. Until now, there has been consideration of CP exclusively within the functional
cycle of perception–cognition–action and it has not been considered the possibility to extend this kind of phenomena to the
mere physiological level. To generalise the notion of CP in this sense, I have proposed to distinguish between categorical
perception (CP) and categorical sensing (CS) in order to extend the CP framework to all communication processes in living
systems, including intracellular, intercellular, metabolic, physiological, cognitive and ecological levels. The main idea
is to provide an account that considers the heterarchical embeddedness of many instances of CP and CS. This will take me to relate the hierarchical nature of categorical sensing and perception
with the equally hierarchical issues of the “binding problem”, “triadic causality”, the “emergent interpretant” and the increasing
semiotic freedom observed in biological and cognitive systems.
相似文献
Luis Emilio BruniEmail: |
11.
Stig S. Gezelius 《Human ecology: an interdisciplinary journal》2007,35(5):587-599
While economic literature inspired by the “tragedy of the commons” has emphasised people’s tendency to increase fishing effort
beyond desirable levels, sociologists and anthropologists who have studied the social aspects of fishing have often emphasised
the capacity of these factors to restrict fishing effort. The article addresses the influence of social norms and communication
on fishing effort in an empirical study of the Atlantic blue whiting fishery. The data were generated at a time when this
fishery had yet to see efficient quota regulations, and had been subject to a rapid growth in fishing effort, making it the
largest fishery in the Atlantic. The article argues that social norms and communication patterns in the fishing fleet create
a synergic effect of co-operation and competition on fishing effort. The article questions the view that social norms and
communication necessarily represent a solution to the tragedy of the commons.
相似文献
Stig S. GezeliusEmail: |
12.
Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
13.
Managing Plant Resources: How Intensive Can it be? 总被引:3,自引:2,他引:1
Martha Sofía González-Insuasti Javier Caballero 《Human ecology: an interdisciplinary journal》2007,35(3):303-314
Previous studies have shown there is a wide spectrum of incipient management practices between gathering and agriculture,
that include resources commonly considered “wild.” Based on the study of 20 species used as foodstuffs in the community of
Santa María Tecomavaca (Mexico), we evaluated nonagricultural management forms such as gathering, incipient nonselective management,
incipient selective management and occasional ex situ cultivation to learn if they represent a gradient in the intensity of manipulation of a resource. The way in which the intensity
of manipulation of a resource can vary as a function of cultural importance and the species’ biology was also analyzed. Using
an index that measures the intensity of management of a resource, it has been established that the degree of intensity depends
on: the specialization of the practices directed to the environment as well as to the individuals; the number of persons performing
these practices; and the number of different practices taking place. The degree of management intensity is also a consequence
of the joint action of cultural importance and of species’ biology.
相似文献
Martha Sofía González-InsuastiEmail: |
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Debates over adaptationism can be clarified and partially resolved by careful consideration of the ‘grain’ at which evolutionary
processes are described. The framework of ‘adaptive landscapes’ can be used to illustrate and facilitate this investigation.
We argue that natural selection may have special status at an intermediate grain of analysis of evolutionary processes. The
cases of sickle-cell disease and genomic imprinting are used as case studies.
相似文献
Peter Godfrey-SmithEmail: |
18.
A key point in the analysis of dynamical models of biological systems is to handle systems of relatively high dimensions.
In the present paper we propose a method to hierarchically organize a certain type of piecewise affine (PWA) differential
systems. This specific class of systems has been extensively studied for the past few years, as it provides a good framework
to model gene regulatory networks. The method, shown on several examples, allows a qualitative analysis of the asymptotic
behavior of a PWA system, decomposing it into several smaller subsystems. This technique, based on the well-known strongly
connected components decomposition, is not new. However, its adaptation to the non-smooth PWA differential equations turns
out to be quite relevant because of the strong discrete structure underlying these equations. Its biological relevance is
shown on a 7-dimensional PWA system modeling the gene network responsible for the carbon starvation response in Escherichia coli.
相似文献
Laurent Tournier (Corresponding author)Email: |
Jean-Luc GouzéEmail: |
19.
Airborne pollen sampling in a wildlife reserve in the south of Buenos Aires province,Argentina 总被引:2,自引:2,他引:0
María Gabriela Murray Rosemary L. Scoffield Carmen Galán Carlos B. Villamil 《Aerobiologia》2007,23(2):107-117
The objective of this project was to study the pollen spectrum of the Marahué Wildlife Reserve (Central Argentina), the quantity
and quality of airborne pollen grains, and to evaluate the contribution of outside sources, to protect a natural habitat with
xerophytic shrub vegetation (“monte”) (the term “monte” is used for the dominant xerophytic shrub vegetation in the “partido”
of Villarino) approximately 90 km south of Bahía Blanca. Sampling was performed weekly throughout a whole calendar year (January–December,
2003) using a volumetric impact sampler. Observations of flowering in the field were performed at the same time as the aerial
sampling. Herbarium specimens were collected to make pollen collections of the species found in the study area, for reference
purposes. The most abundant pollen types were Poaceae (31.3% total annual pollen), Amaranthus/Chenopodiaceae (25.3%), Eucalyptus (5%), Brassicaceae (3.9%), and Plantago (3.9%). This study showed the dispersion dynamics of pollen grains from characteristic species of the “partido” (the province
of Buenos Aires is divided into partidos which are roughly equivalent to counties) of Villarino, the exotic flora of the surrounding
area, and the pollen types from outside the region.
相似文献
María Gabriela MurrayEmail: |
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