485 research outputs found
Constructing virtual 5-dimensional tori out of lower-dimensional network cards
[EN] In the Top500 and Graph500 lists of the last years, some of the most powerful systems implement
a torus topology to interconnect themillions of computing nodes they include. Some of these torus
networks are of five or six dimensions, which implies an additional difficulty as the node degree
increases. In previous works, we proposed and evaluated the nD Twin (nDT) torus topology to virtually
increase the dimensions a torus is able to implement. We showed that this new topology
reduces the distances between nodes, increasing, therefore, global network performance. In this
work, we present how to build a 5DT torus network using a specific commercial 6-port network
card (EXTOLL card) to interconnect those nodes. We show, using the same number of cards, that
the performance of the 5DT torus network we are able to implement using our proposal is higher
than the performance of the 3D torus network for the same number of compute nodes.Spanish MINECO; European Commission, Grant/Award Number: TIN2015-66972-C5-1-R and TIN2015-66972-C5-2-R; JCCM, Grant/Award Number: PEII-2014-028-P; Spanish MICINN, Grant/Award Number: FJCI-2015-26080AndĂşjar-Muñoz, FJ.; Villar, JA.; Sanchez Garcia, JL.; Alfaro Cortes, FJ.; Duato MarĂn, JF.; Fröning, H. (2017). Constructing virtual 5-dimensional tori out of lower-dimensional network cards. Concurrency and Computation Practice and Experience. 1-17. https://doi.org/10.1002/cpe.4361S11
Small-world interconnection networks for large parallel computer systems
The use of small-world graphs as interconnection networks of multicomputers is proposed and analysed in this work. Small-world interconnection networks are constructed by adding (or modifying) edges to an underlying local graph. Graphs with a rich local structure but with a large diameter are shown to be the most suitable candidates for the underlying graph. Generation models based on random and deterministic wiring processes are proposed and analysed. For the random case basic properties such as degree, diameter, average length and bisection width are analysed, and the results show that a fast transition from a large diameter to a small diameter is experienced when the number of new edges introduced is increased. Random traffic analysis on these networks is undertaken, and it is shown that although the average latency experiences a similar reduction, networks with a small number of shortcuts have a tendency to saturate as most of the traffic flows through a small number of links. An analysis of the congestion of the networks corroborates this result and provides away of estimating the minimum number of shortcuts required to avoid saturation. To overcome these problems deterministic wiring is proposed and analysed. A Linear Feedback Shift Register is used to introduce shortcuts in the LFSR graphs. A simple routing algorithm has been constructed for the LFSR and extended with a greedy local optimisation technique. It has been shown that a small search depth gives good results and is less costly to implement than a full shortest path algorithm. The Hilbert graph on the other hand provides some additional characteristics, such as support for incremental expansion, efficient layout in two dimensional space (using two layers), and a small fixed degree of four. Small-world hypergraphs have also been studied. In particular incomplete hypermeshes have been introduced and analysed and it has been shown that they outperform the complete traditional implementations under a constant pinout argument. Since it has been shown that complete hypermeshes outperform the mesh, the torus, low dimensional m-ary d-cubes (with and without bypass channels), and multi-stage interconnection networks (when realistic decision times are accounted for and with a constant pinout), it follows that incomplete hypermeshes outperform them as well
An Email Attachment is Worth a Thousand Words, or Is It?
There is an extensive body of research on Social Network Analysis (SNA) based
on the email archive. The network used in the analysis is generally extracted
either by capturing the email communication in From, To, Cc and Bcc email
header fields or by the entities contained in the email message. In the latter
case, the entities could be, for instance, the bag of words, url's, names,
phones, etc. It could also include the textual content of attachments, for
instance Microsoft Word documents, excel spreadsheets, or Adobe pdfs. The nodes
in this network represent users and entities. The edges represent communication
between users and relations to the entities. We suggest taking a different
approach to the network extraction and use attachments shared between users as
the edges. The motivation for this is two-fold. First, attachments represent
the "intimacy" manifestation of the relation's strength. Second, the
statistical analysis of private email archives that we collected and Enron
email corpus shows that the attachments contribute in average around 80-90% to
the archive's disk-space usage, which means that most of the data is presently
ignored in the SNA of email archives. Consequently, we hypothesize that this
approach might provide more insight into the social structure of the email
archive. We extract the communication and shared attachments networks from
Enron email corpus. We further analyze degree, betweenness, closeness, and
eigenvector centrality measures in both networks and review the differences and
what can be learned from them. We use nearest neighbor algorithm to generate
similarity groups for five Enron employees. The groups are consistent with
Enron's organizational chart, which validates our approach.Comment: 12 pages, 4 figures, 7 tables, IML'17, Liverpool, U
Armstrong Research, Technology, and Engineering Accomplishments 2014
No abstract availabl
Reliable low latency I/O in torus-based interconnection networks
In today's high performance computing environment I/O remains the main bottleneck in
achieving the optimal performance expected of the ever improving processor and
memory technologies. Interconnection networks therefore combines processing units,
system I/O and high speed switch network fabric into a new paradigm of I/O based
network. It decouples the system into computational and I/O interconnections each
allowing "any-to-any" communications among processors and I/O devices unlike the
shared model in bus architecture. The computational interconnection, a network of
processing units (compute-nodes), is used for inter-processor communication in carrying
out computation tasks, while the I/O interconnection manages the transfer of I/O requests
between the compute-nodes and the I/O or storage media through some dedicated I/O
processing units (I /O-nodes). Considering the special functions performed by the I/O
nodes, their placement and reliability become important issues in improving the overall
performance of the interconnection system.
This thesis focuses on design and topological placement of I/O-nodes in torus based
interconnection networks, with the aim of reducing I/O communication latency between
compute-nodes and I/O-nodes even in the presence of faulty I/O-nodes. We propose an
efficient and scalable relaxed quasi-perfect placement scheme using Lee distance error
correction code such that compute-nodes are at distance-t or at most distance-t+1 from an
I/O-node for a given t. This scheme provides a better and optimal alternative placement
than quasi perfect placement when perfect placement cannot be found for a particular
torus. Furthermore, in the occurrence of faulty I/O-nodes, the placement scheme is also
used in determining other alternative I/O-nodes for rerouting I/O traffic from affected
compute-nodes with minimal slowdown. In order to guarantee the quality of service
required of inter-processor communication, a scheduling algorithm was developed at the router level to prioritize message forwarding according to inter-process and I/O messages
with the former given higher priority.
Our simulation results show that relaxed quasi-perfect outperforms quasi-perfect and the
conventional I/O placement (where I/O nodes are concentrated at the base of the torus
interconnection) with little degradation in inter-process communication performance.
Also the fault tolerant redirection scheme provides a minimal slowdown, especially when
the number of faulty I/O nodes is less than half of the initial available I/O nodes
Rehabilitation Engineering
Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device
2019 Undergraduate Research Symposium: Full Program
Full program with schedule and abstracts for the 2019 Undergraduate Research Symposium
Virtual Reality Games for Motor Rehabilitation
This paper presents a fuzzy logic based method to track user satisfaction without the need for devices to monitor users physiological conditions. User satisfaction is the key to any product’s acceptance; computer applications and video games provide a unique opportunity to provide a tailored environment for each user to better suit their needs. We have implemented a non-adaptive fuzzy logic model of emotion, based on the emotional component of the Fuzzy Logic Adaptive Model of Emotion (FLAME) proposed by El-Nasr, to estimate player emotion in UnrealTournament 2004. In this paper we describe the implementation of this system and present the results of one of several play tests. Our research contradicts the current literature that suggests physiological measurements are needed. We show that it is possible to use a software only method to estimate user emotion
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