2,070 research outputs found
A compiler approach to scalable concurrent program design
The programmer's most powerful tool for controlling complexity in program design is abstraction. We seek to use abstraction in the design of concurrent programs, so as to
separate design decisions concerned with decomposition, communication, synchronization, mapping, granularity, and load balancing. This paper describes programming and compiler techniques intended to facilitate this design strategy. The programming techniques are based on a core programming notation with two important properties: the ability to separate concurrent programming concerns, and extensibility with reusable programmer-defined
abstractions. The compiler techniques are based on a simple transformation system together with a set of compilation transformations and portable run-time support. The
transformation system allows programmer-defined abstractions to be defined as source-to-source transformations that convert abstractions into the core notation. The same
transformation system is used to apply compilation transformations that incrementally transform the core notation toward an abstract concurrent machine. This machine can be implemented on a variety of concurrent architectures using simple run-time support.
The transformation, compilation, and run-time system techniques have been implemented and are incorporated in a public-domain program development toolkit. This
toolkit operates on a wide variety of networked workstations, multicomputers, and shared-memory
multiprocessors. It includes a program transformer, concurrent compiler, syntax checker, debugger, performance analyzer, and execution animator. A variety of substantial
applications have been developed using the toolkit, in areas such as climate modeling and fluid dynamics
Replica Selection in the Globus Data Grid
The Globus Data Grid architecture provides a scalable infrastructure for the
management of storage resources and data that are distributed across Grid
environments. These services are designed to support a variety of scientific
applications, ranging from high-energy physics to computational genomics, that
require access to large amounts of data (terabytes or even petabytes) with
varied quality of service requirements. By layering on a set of core services,
such as data transport, security, and replica cataloging, one can construct
various higher-level services. In this paper, we discuss the design and
implementation of a high-level replica selection service that uses information
regarding replica location and user preferences to guide selection from among
storage replica alternatives. We first present a basic replica selection
service design, then show how dynamic information collected using Globus
information service capabilities concerning storage system properties can help
improve and optimize the selection process. We demonstrate the use of Condor's
ClassAds resource description and matchmaking mechanism as an efficient tool
for representing and matching storage resource capabilities and policies
against application requirements.Comment: 8 pages, 6 figure
Occurrence and Behavior of Juvenile Red Snapper, Lutjanus campechanus, on Commercial Shrimp Fishing Grounds in the Northeastern Gulf of Mexico
Red snapper, Lutjanus campechanus, is subject to significant overfishing in U.S. Gulf of Mexico waters, and regulations are being implemented to reduce fishing mortality and restore them to a 20% spawning potential ratio by the year 2009. One source of mortality that must be reduced to achieve this goal is the incidental capture ofjuvenile red snappers in shrimp, Penaeus spp., trawls. NOAA's National Marine Fisheries Service is conducting research to develop shrimp trawl modifications to reduce the snapper bycatch. An important part of this research is the study of juvenile red snapper behavior on commercial shrimp grounds and in relation to trawling gear.
An area of high juvenile red snapper abundance was identified off the coast of Mississippi. Most snappers were observed around structures or objects on the bottom which they appeared to use for refuge or orientation. Those ranging over barren bottom had no apparent point of orientation. When encountered by shrimp trawls, most juvenile snappers rose above the trawl footrope and fell back into the trawl. These observations have directed research toward modifying shrimp trawls to release juvenile red snappers after entry, rather than preventing them from entering a shrimp trawl
Small-World File-Sharing Communities
Web caches, content distribution networks, peer-to-peer file sharing
networks, distributed file systems, and data grids all have in common that they
involve a community of users who generate requests for shared data. In each
case, overall system performance can be improved significantly if we can first
identify and then exploit interesting structure within a community's access
patterns. To this end, we propose a novel perspective on file sharing based on
the study of the relationships that form among users based on the files in
which they are interested.
We propose a new structure that captures common user interests in data--the
data-sharing graph-- and justify its utility with studies on three
data-distribution systems: a high-energy physics collaboration, the Web, and
the Kazaa peer-to-peer network. We find small-world patterns in the
data-sharing graphs of all three communities. We analyze these graphs and
propose some probable causes for these emergent small-world patterns. The
significance of small-world patterns is twofold: it provides a rigorous support
to intuition and, perhaps most importantly, it suggests ways to design
mechanisms that exploit these naturally emerging patterns
The Role of Superannuation in the Financial Sector and in Aggregate Saving: A Review of Recent Trends
Assets with superannuation funds represented the fastest growing of the major components of household wealth during the 1980s. This paper reviews the causes of that growth, and its effects on private saving and on the pattern of financial intermediation. It is found that the growth of superannuation funds during this period was mainly a result of the funds’ high earnings rates; there was relatively little change in the net rate of new contributions by members. This fact makes it hard to argue that growth of the superannuation sector came at the expense of other types of financial intermediaries. The relative stability of members’ contributions also helps to explain why superannuation has not yet had a noticeable effect on the level of private saving.
DiPerF: an automated DIstributed PERformance testing Framework
We present DiPerF, a distributed performance testing framework, aimed at
simplifying and automating service performance evaluation. DiPerF coordinates a
pool of machines that test a target service, collects and aggregates
performance metrics, and generates performance statistics. The aggregate data
collected provide information on service throughput, on service "fairness" when
serving multiple clients concurrently, and on the impact of network latency on
service performance. Furthermore, using this data, it is possible to build
predictive models that estimate a service performance given the service load.
We have tested DiPerF on 100+ machines on two testbeds, Grid3 and PlanetLab,
and explored the performance of job submission services (pre WS GRAM and WS
GRAM) included with Globus Toolkit 3.2.Comment: 8 pages, 8 figures, will appear in IEEE/ACM Grid2004, November 200
What brings the first rains of the season?
There are two major sources of rainfall over south-western Australia
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