Progress on Perfect Lattice Actions for QCD

We describe a number of aspects in our attempt to construct an approximately perfect lattice action for QCD. Free quarks are made optimally local on the whole renormalized trajectory and their couplings are then truncated by imposing 3-periodicity. The spectra of these short ranged fermions are excellent approximations to continuum spectra. The same is true for free gluons. We evaluate the corresponding perfect quark-gluon vertex function, identifying in particular the ``perfect clover term''. First simulations for heavy quarks show that the mass is strongly renormalized, but again the renormalized theory agrees very well with continuum physics. Furthermore we describe the multigrid formulation for the non-perturbative perfect action and we present the concept of an exactly (quantum) perfect topological charge on the lattice.Comment: 14 pages, 17 figures, Talk presented at LATTICE96(improvement

Passive characterization of sopcast usage in residential ISPs

Abstract—In this paper we present an extensive analysis of traffic generated by SopCast users and collected from operative networks of three national ISPs in Europe. After more than a year of continuous monitoring, we present results about the popularity of SopCast which is the largely preferred application in the studied networks. We focus on analysis of (i) application and bandwidth usage at different time scales, (ii) peer lifetime, arrival and departure processes, (iii) peer localization in the world. Results provide useful insights into users ’ behavior, including their attitude towards P2P-TV application usage and the conse-quent generated load on the network, that is quite variable based on the access technology and geographical location. Our findings are interesting to Researchers interested in the investigation of users ’ attitude towards P2P-TV services, to foresee new trends in the future usage of the Internet, and to augment the design of their application. I

HLOC: Hints-Based Geolocation Leveraging Multiple Measurement Frameworks

Geographically locating an IP address is of interest for many purposes. There are two major ways to obtain the location of an IP address: querying commercial databases or conducting latency measurements. For structural Internet nodes, such as routers, commercial databases are limited by low accuracy, while current measurement-based approaches overwhelm users with setup overhead and scalability issues. In this work we present our system HLOC, aiming to combine the ease of database use with the accuracy of latency measurements. We evaluate HLOC on a comprehensive router data set of 1.4M IPv4 and 183k IPv6 routers. HLOC first extracts location hints from rDNS names, and then conducts multi-tier latency measurements. Configuration complexity is minimized by using publicly available large-scale measurement frameworks such as RIPE Atlas. Using this measurement, we can confirm or disprove the location hints found in domain names. We publicly release HLOC's ready-to-use source code, enabling researchers to easily increase geolocation accuracy with minimum overhead.Comment: As published in TMA'17 conference: http://tma.ifip.org/main-conference

A fine-grain time-sharing Time Warp system

Although Parallel Discrete Event Simulation (PDES) platforms relying on the Time Warp (optimistic) synchronization protocol already allow for exploiting parallelism, several techniques have been proposed to further favor performance. Among them we can mention optimized approaches for state restore, as well as techniques for load balancing or (dynamically) controlling the speculation degree, the latter being specifically targeted at reducing the incidence of causality errors leading to waste of computation. However, in state of the art Time Warp systems, events’ processing is not preemptable, which may prevent the possibility to promptly react to the injection of higher priority (say lower timestamp) events. Delaying the processing of these events may, in turn, give rise to higher incidence of incorrect speculation. In this article we present the design and realization of a fine-grain time-sharing Time Warp system, to be run on multi-core Linux machines, which makes systematic use of event preemption in order to dynamically reassign the CPU to higher priority events/tasks. Our proposal is based on a truly dual mode execution, application vs platform, which includes a timer-interrupt based support for bringing control back to platform mode for possible CPU reassignment according to very fine grain periods. The latter facility is offered by an ad-hoc timer-interrupt management module for Linux, which we release, together with the overall time-sharing support, within the open source ROOT-Sim platform. An experimental assessment based on the classical PHOLD benchmark and two real world models is presented, which shows how our proposal effectively leads to the reduction of the incidence of causality errors, as compared to traditional Time Warp, especially when running with higher degrees of parallelism

Analysis and Approximation of Optimal Co-Scheduling on CMP

In recent years, the increasing design complexity and the problems of power and heat dissipation have caused a shift in processor technology to favor Chip Multiprocessors. In Chip Multiprocessors (CMP) architecture, it is common that multiple cores share some on-chip cache. The sharing may cause cache thrashing and contention among co-running jobs. Job co-scheduling is an approach to tackling the problem by assigning jobs to cores appropriately so that the contention and consequent performance degradations are minimized. This dissertation aims to tackle two of the most prominent challenges in job co-scheduling.;The first challenge is in the computational complexity for determining optimal job co-schedules. This dissertation presents one of the first systematic analyses on the complexity of job co-scheduling. Besides proving the NP completeness of job co-scheduling, it introduces a set of algorithms, based on graph theory and Integer/Linear Programming, for computing optimal co-schedules or their lower bounds in scenarios with or without job migrations. For complex cases, it empirically demonstrates the feasibility for approximating the optimal schedules effectively by proposing several heuristics-based algorithms. These discoveries facilitate the assessment of job co-schedulers by providing necessary baselines, and shed insights to the development of practical co-scheduling systems.;The second challenge resides in the prediction of the performance of processes co-running on a shared cache. This dissertation explores the influence on co-run performance prediction imposed by co-runners, program inputs, and cache configurations. Through a sequence of formal analysis, we derive an analytical co-run locality model, uncovering the inherent statistical connections between the data references of programs single-runs and their co-run locality. The model offers theoretical insights on co-run locality analysis and leads to a lightweight approach for fast prediction of shared cache performance. We demonstrate the effectiveness of the model in enabling proactive job co-scheduling.;Together, the two-dimensional findings open up many new opportunities for cache management on modern CMP by laying the foundation for job co-scheduling, and enhancing the understanding to data locality and cache sharing significantly

Willingness to pay for outpatient services user fees: Malaysian community perspective

Health care services are not often accessible and available for all people in one country due to multiple reasons such as the geographical barrier, affordability, etc. The aim of this study was to analyse willingness to pay (WTP) for healthcare services user fees among Malaysian population and determine its’ influencing factors. Structured interviews were conducted involving 774 households in 4 states represents Peninsular Malaysia. Validated questionnaires with open ended, followed by bidding games were applied to elicit maximum amount of WTP. The study was analysed descriptively and with multivariate regression method to adjust for potential confounding factors. More than half of respondents WTP more than current fee for the government clinic outpatient registration fee with mean MYR3.76 (SD2.71). Majority of respondents not WTP more than usual for private clinic simple outpatient treatment charges with the mean MYR38.76 (SD5.45). Factors that were found to have significant associations with WTP for both government and private clinic were income and having health insurance. Community willing to pay for healthcare services user fees and charges but at certain amount. The healthcare services user fees and charges can be increased up to community WTP level to avoid from catastrophic expenditure