7,386 research outputs found
A Modular and Fault-Tolerant Data Transport Framework
The High Level Trigger (HLT) of the future ALICE heavy-ion experiment has to
reduce its input data rate of up to 25 GB/s to at most 1.25 GB/s for output
before the data is written to permanent storage. To cope with these data rates
a large PC cluster system is being designed to scale to several 1000 nodes,
connected by a fast network. For the software that will run on these nodes a
flexible data transport and distribution software framework, described in this
thesis, has been developed. The framework consists of a set of separate
components, that can be connected via a common interface. This allows to
construct different configurations for the HLT, that are even changeable at
runtime. To ensure a fault-tolerant operation of the HLT, the framework
includes a basic fail-over mechanism that allows to replace whole nodes after a
failure. The mechanism will be further expanded in the future, utilizing the
runtime reconnection feature of the framework's component interface. To connect
cluster nodes a communication class library is used that abstracts from the
actual network technology and protocol used to retain flexibility in the
hardware choice. It contains already two working prototype versions for the TCP
protocol as well as SCI network adapters. Extensions can be added to the
library without modifications to other parts of the framework. Extensive tests
and measurements have been performed with the framework. Their results as well
as conclusions drawn from them are also presented in this thesis. Performance
tests show very promising results for the system, indicating that it can
fulfill ALICE's requirements concerning the data transport.Comment: Ph.D. Thesis, Ruprecht-Karls-University Heidelberg Large, 251 page
Reliability and fault tolerance in the European ADS project
After an introduction to the theory of reliability, this paper focuses on a
description of the linear proton accelerator proposed for the European ADS
demonstration project. Design issues are discussed and examples of cases of
fault tolerance are given.Comment: 14 pages, contribution to the CAS - CERN Accelerator School: Course
on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai
What is a quantum computer, and how do we build one?
The DiVincenzo criteria for implementing a quantum computer have been seminal
in focussing both experimental and theoretical research in quantum information
processing. These criteria were formulated specifically for the circuit model
of quantum computing. However, several new models for quantum computing
(paradigms) have been proposed that do not seem to fit the criteria well. The
question is therefore what are the general criteria for implementing quantum
computers. To this end, a formal operational definition of a quantum computer
is introduced. It is then shown that according to this definition a device is a
quantum computer if it obeys the following four criteria: Any quantum computer
must (1) have a quantum memory; (2) facilitate a controlled quantum evolution
of the quantum memory; (3) include a method for cooling the quantum memory; and
(4) provide a readout mechanism for subsets of the quantum memory. The criteria
are met when the device is scalable and operates fault-tolerantly. We discuss
various existing quantum computing paradigms, and how they fit within this
framework. Finally, we lay out a roadmap for selecting an avenue towards
building a quantum computer. This is summarized in a decision tree intended to
help experimentalists determine the most natural paradigm given a particular
physical implementation
Real Time Global Tests of the ALICE High Level Trigger Data Transport Framework
The High Level Trigger (HLT) system of the ALICE experiment is an online
event filter and trigger system designed for input bandwidths of up to 25 GB/s
at event rates of up to 1 kHz. The system is designed as a scalable PC cluster,
implementing several hundred nodes. The transport of data in the system is
handled by an object-oriented data flow framework operating on the basis of the
publisher-subscriber principle, being designed fully pipelined with lowest
processing overhead and communication latency in the cluster. In this paper, we
report the latest measurements where this framework has been operated on five
different sites over a global north-south link extending more than 10,000 km,
processing a ``real-time'' data flow.Comment: 8 pages 4 figure
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