Performance Evaluation of JXTA Communication layers

The main goal of Project JXTA is to provide a peer-to-peer application framework based on a standard set of generic peer-to-peer protocols, independent of any particular platform or language. In spite of its recent popularity, the performance characteristics of the communication layers of JXTA are not well understood, though there is a general sentiment of inadequate performance. This paper examines the performance of the three JXTA communication layers: the JXTA sockets, JXTA pipe service and JXTA endpoint service. Round-trip time benchmarks are performed to evaluate the bandwidth and latency of each of the communication layers over both a Fast-Ethernet and a Myrinet network using the Java implementation of the JXTA protocols. The results show that, although the JXTA communications exhibit high latency, the Java binding of JXTA is able to reach the throughput of Java sockets. Very interesting results were obtained for benchmarks performed on high-performance Myrinet networks, where two out of the three JXTA communication layers were still able to achieve throughputs in excess of 1 Gb/s

Short-term Farm Level Adaptations of EU15 Agricultural Supply to Climate Change

Assessing climate change impact on agriculture is a complex task involving a wide range of economical and physical processes, leading to significant uncertainties. At European scale, climate change impacts on agricultural supply have been appraised to be of relatively less important driver by the end of century compared to other global drivers. However these diagnoses are incomplete due to a limited representation of both spatial heterogeneity in important determinants of agricultural supply (soil, management practices and producer typology) and fine scale processes such as farm scale autonomous adaptation. We propose a complementary approach based on a modeling framework including a spatially explicit representation of productivity and producer behavior with regard to heterogeneity in soil, climate, and producer socio-economic context to appraise climate change impacts including autonomous farm-scale adaptations of EU15 agricultural supply to climate change. Our results suggest that without accounting for autonomous adaptation European agricultural supply may have interesting resilience properties at an aggregated scale despite significant heterogeneity at smaller resolution. Accounting for autonomous adaptations result in significant yield gains, and may lead to (i) a significant increase in the relative profitability of crops compared to other land-covers, thus possibly increasing its agricultural land-use share over other land covers, and (ii) an increase in total European production which may have impacts on agricultural goods markets, thus highlighting the need for integrating fine scale processes such as autonomous adaptation.Environmental Economics and Policy, Farm Management,

MojaveComm: A Robust Group Communication Library for Grid Environments

This paper introduces a fault-tolerant group communication protocol that is aimed at grid and wide area environments. The protocol has two layers. The lower layer provides a total order of messages in one group, while the upper layer provides an ordering of messages across groups. The protocol can be used to implement sequential consistency. To prove the correctness of our protocol we have used a combination of model checking and mathematical proofs. The paper also presents the behavior of our implementation of the protocol in a simulated environment

QUANTIFYING THE HETEROGENEITY OF ABATEMENT COSTS UNDER CLIMATIC AND ENVIRONMENTAL REGULATION CHANGES: AN INTEGRATED MODELLING APPROACH

We present here preliminary results of an integrated modelling approach combining a crop model (STICS) and an economic model (AROPAj) of European agricultural supply. This modelling framework is designed to perform quantitative analysis, regarding climate change impacts on agriculture and more generally the interactions between soils, land use, agriculture and climate integrating physical and economical elements (data, process, models). It explicitly integrates an agricultural diversity dimension with regards to economic set of choices and soil climate spatial variability. First results are given in term of quantitative analysis combining optimal land allocation (economic optimality) and “dose-response” functions related to a large set of crops in Europe, at the farm group level, covering part of the European Union (EU15). They indicate that accounting for economical and spatial variability may impact both regional aggregated scales results.Crop Production/Industries, Environmental Economics and Policy, International Relations/Trade, Land Economics/Use, Resource /Energy Economics and Policy,

Enabling JXTA for High Performance Grid Computing

Grid computing has recently emerged as a response to the growing demand for resources (processing power, storage, etc.) exhibited by scientific applications. However, as grid sizes increase, the need for self-organization and dynamic reconfigurations is becoming more and more important. Since such properties are exhibited by P2P systems, the convergence of grid computing and P2P computing seems natural. However, using P2P systems (usually running on the Internet) on a grid infrastructure (generally available as a federation of SAN-based clusters interconnected by high-bandwidth WANs) may raise the issue of the adequacy of the P2P communication mechanisms. This paper evaluates the communication performance of the JXTA P2P library over SANs and WANs, for both J2SE and C bindings. We analyze these results and we evaluate solutions able to improve the performance of JXTA on such grid infrastructures

Implementation and evaluation of physiotherapist independent prescribing: a mixed multi-methods analysis

This research presents novel knowledge and insight into the effective implementation and utilisation of non-medical prescribing (NMP) across professions internationally. It will inform safe and effective implementation of physiotherapy independent prescribing across clinical specialities, settings and jurisdictions. Individual studies (systematic reviews, surveys, feasibility trial) were designed using rigorous mixed methods, addressing specific pre-determined aims and objectives generated from gaps in the literature. Rigorous evaluation established that the benefit of NMP to the health economy remains unclear and limited evidence exists evaluating its clinical effectiveness across professions and clinical settings. Internationally, physiotherapists support the introduction of physiotherapist prescribing. Physiotherapists surveyed in Australia perceived potential benefits across the population, within a multimodal-physiotherapeutic context. Barriers and facilitators of the implementation/utilisation of NMP demonstrate multifactorial context specific variables. The resulting implementation framework may be useful to aid safe and successful implementation/utilisation of NMP. Low risk of bias trials are required to evaluate the clinical and cost-effectiveness of physiotherapist prescribing across a range of clinical specialities and settings. High-quality feasibility trial data demonstrates that with minor modifications, a low risk of bias trial to evaluate clinical and cost-effectiveness of physiotherapist independent prescribing for low back pain in primary care is feasible, suitable and acceptable

A practical example of convergence of P2P and grid computing: an evaluation of JXTA's communication performance on grid networking infrastructures

International audienceAs the size of today's grid computing platforms increases, the need for self-organization and dynamic reconfiguration becomes more and more important. In this context, the convergence of grid computing and peer-to-peer (P2P) computing seems natural. However, grid infrastructures are generally available as a hierarchical federation of SAN-based clusters interconnected by high-bandwidth WANs. In contrast, P2P systems usually run on the Internet, on top of random, generally flat network topologies. This difference may lead to the legitimate question of how adequate are the P2P communication mechanisms on hierarchical grid infrastructures. Answering this question is important, since it is essential to efficiently exploit the particular features of grid networking topologies in order to meet the constraints of scientific applications. This paper evaluates the communication performance of the JXTA P2P platform over high-performance SANs and WANs, for both J2SE and C bindings. We discuss these results, then we propose and evaluate several techniques able to improve the JXTA's performance on such grid networking infrastructures