121 research outputs found
Task swapping networks in distributed systems
In this paper we propose task swapping networks for task reassignments by
using task swappings in distributed systems. Some classes of task reassignments
are achieved by using iterative local task swappings between software agents in
distributed systems. We use group-theoretic methods to find a minimum-length
sequence of adjacent task swappings needed from a source task assignment to a
target task assignment in a task swapping network of several well-known
topologies.Comment: This is a preprint of a paper whose final and definite form is
published in: Int. J. Comput. Math. 90 (2013), 2221-2243 (DOI:
10.1080/00207160.2013.772985
CLEX: Yet Another Supercomputer Architecture?
We propose the CLEX supercomputer topology and routing scheme. We prove that
CLEX can utilize a constant fraction of the total bandwidth for point-to-point
communication, at delays proportional to the sum of the number of intermediate
hops and the maximum physical distance between any two nodes. Moreover, %
applying an asymmetric bandwidth assignment to the links, all-to-all
communication can be realized -optimally both with regard to
bandwidth and delays. This is achieved at node degrees of ,
for an arbitrary small constant . In contrast, these
results are impossible in any network featuring constant or polylogarithmic
node degrees. Through simulation, we assess the benefits of an implementation
of the proposed communication strategy. Our results indicate that, for a
million processors, CLEX can increase bandwidth utilization and reduce average
routing path length by at least factors respectively in comparison to
a torus network. Furthermore, the CLEX communication scheme features several
other properties, such as deadlock-freedom, inherent fault-tolerance, and
canonical partition into smaller subsystems
OREGAMI: Software Tools for Mapping Parallel Computations to Parallel Architectures
22 pagesThe mapping problem in message-passing parallel processors involves
the assignment of tasks in a parallel computation to processors and the
routing of inter-task messages along the links of the interconnection network.
We have developed a unified set of software tools called OREGAMI
for automatic and guided mapping of parallel computations to parallel architectures
in order to achieve portability and maximal performance from
parallel systems. Our tools include a description language which enables
the programmer of parallel algorithms to specify information about the
static and dynamic communication behavior of the computation to be
mapped. This information is used by the mapping algorithms to assign
tasks to processors and to route communication in the network topology.
Two key features of our system are (a) the ability to take advantage of
the regularity present in both the computation structure and the interconnection
network and (b) the desire to balance the user's knowledge
and intuition with the computational power of efficient combinatorial algorithms
Algebraic and Computer-based Methods in the Undirected Degree/diameter Problem - a Brief Survey
This paper discusses the most popular algebraic techniques and computational methods that have been used to construct large graphs with given degree and diameter
Analysis of wormhole routings in cayley graphs of permutation groups.
Over a decade, a new class of switching technology, called wormhole routing, has been investigated in the multicomputer interconnection network field. Several classes of wormhole routing algorithms have been proposed. Most of the algorithms have been centered on the traditional binary hypercube, k-ary n-cube mesh, and torus networks. In the design of a wormhole routing algorithm, deadlock avoidance scheme is the main concern. Recently, new classes of networks called Cayley graphs of permutation groups are considered very promising alternatives. Although proposed Cayley networks have superior topological properties over the traditional network topologies, the design of the deadlock-free wormhole routing algorithm in these networks is not simple. In this dissertation, we investigate deadlock free wormhole routing algorithms in the several classes of Cayley networks, such as complete-transposition and star networks. We evaluate several classes of routing algorithms on these networks, and compare the performance of each algorithm to the simulation study. Also, the performances of these networks are compared to the traditional networks. Through extensive simulation we found that adaptive algorithm outperformed deterministic algorithm in general with more virtual channels. On the network performance comparison, the complete transposition network showed the best performance among the similar sized networks, and the binary hypercube performed better compared to the star graph
Quarc: an architecture for efficient on-chip communication
The exponential downscaling of the feature size has enforced a paradigm shift from computation-based design to communication-based design in system on chip development. Buses, the traditional communication architecture in systems on chip, are incapable of addressing the increasing bandwidth requirements of future large systems.
Networks on chip have emerged as an interconnection architecture offering unique solutions to the technological and design issues related to communication in future systems on chip. The transition from buses as a shared medium to networks on chip as a segmented medium has given rise to new challenges in system on chip realm.
By leveraging the shared nature of the communication medium, buses have been highly efficient in delivering multicast communication. The segmented nature of networks, however, inhibits the multicast messages to be delivered as efficiently by networks on chip. Relying on extensive research on multicast communication in parallel computers, several network on chip architectures have offered mechanisms to perform the operation, while conforming to resource constraints of the network on chip paradigm. Multicast communication in majority of these networks on chip is implemented by establishing a connection between source and all multicast destinations before the message transmission
commences. Establishing the connections incurs an overhead and, therefore, is not desirable; in particular in latency sensitive services such as cache coherence.
To address high performance multicast communication, this research presents Quarc, a novel network on chip architecture. The Quarc architecture targets an area-efficient, low power, high performance implementation. The thesis covers a detailed representation of
the building blocks of the architecture, including topology, router and network interface.
The cost and performance comparison of the Quarc architecture against other network on chip architectures reveals that the Quarc architecture is a highly efficient architecture.
Moreover, the thesis introduces novel performance models of complex traffic patterns, including multicast and quality of service-aware communication
Wireless Communication in Data Centers: A Survey
Data centers (DCs) is becoming increasingly an integral part of the computing infrastructures of most enterprises. Therefore, the concept of DC networks (DCNs) is receiving an increased attention in the network research community. Most DCNs deployed today can be classified as wired DCNs as copper and optical fiber cables are used for intra- and inter-rack connections in the network. Despite recent advances, wired DCNs face two inevitable problems; cabling complexity and hotspots. To address these problems, recent research works suggest the incorporation of wireless communication technology into DCNs. Wireless links can be used to either augment conventional wired DCNs, or to realize a pure wireless DCN. As the design spectrum of DCs broadens, so does the need for a clear classification to differentiate various design options. In this paper, we analyze the free space optical (FSO) communication and the 60 GHz radio frequency (RF), the two key candidate technologies for implementing wireless links in DCNs. We present a generic classification scheme that can be used to classify current and future DCNs based on the communication technology used in the network. The proposed classification is then used to review and summarize major research in this area. We also discuss open questions and future research directions in the area of wireless DCs
- …