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The Adaptive Bubble Router

The design of a new adaptive virtual cut-through router for torus networks is presented in this paper. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than deterministic wormhole routers based on virtual channels. This has been achieved by combining a low-cost deadlock avoidance mechanism for virtual cut-through networks, called Bubble flow control, with an adequate design of the routers arbiter. A thorough methodology has been employed to quantify the impact that this router design has at all levels, from its hardware cost to the system performance when running parallel applications. At the VLSI level, our proposal is the adaptive router with the shortest clock cycle and node delay when compared with other state-of-the-art alternatives. This translates into the lowest latency and highest throughput under standard synthetic loads. At system level, these gains reduce the execution time of the benchmarks considered. Compared with current adaptive wormhole routers, the execution time is reduced by up to 27%. Furthermore, this is the only router that improves system performance when compared with simpler static designs.

Adaptive bubble router: a design to improve performance in torus networks

A router design for torus networks that significantly reduces message latency over traditional wormhole routers is presented in this paper. This new router implements virtual cut-through switching and fully-adaptive minimal routing. Packet deadlock is avoided by providing escape ways governed by Bubble flow control, a mechanism that guarantees enough free buffer space in the network to allow continuous packet movement. Both deterministic and adaptive Bubble routers have been designed in VLSI using VHDL synthesis tools. Adopting a fair quantitative comparison, we demonstrate that Bubble routers exhibit a reduction in base latency values over 40% with respect to the corresponding wormhole routers, without any penalty in network throughput. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than deterministic wormhole routers based on virtual channels.

Dense Gaussian networks: suitable topologies for on-chip multiprocessors

This paper explores the suitability of dense circulant graphs of degree four for the design of on-chip interconnection networks. Networks based on these graphs reduce the Torus diameter in a factor

Improving parallel system performance by changing the arrangement of the network links

\sqrt{2}

Evaluation of interconnection network performance under heavy non-uniform loads

, which translates into significant performance gains for unicast traffic. In addition, they are clearly superior to Tori when managing collective communications. This paper introduces a new two-dimensional node’s labeling of the networks explored which simplifies their analysis and exploitation. In particular, it provides simple and optimal solutions to two important architectural issues: routing and broadcasting. Other implementation issues such as network folding and scalability by using hierarchical networks are also explored in this work.

A PERFORMANCE EVALUATION OF ADAPTIVE ROUTING IN BIDIMENSIONAL CUT-THROUGH NETWORKS

Interconnection networks in current parallel systems do not only increase in size; their buffer capacity and number of source ports have increased as well. All these factors result in a significant rise of network congestion compared with their predecessors. Consequently, packet injection must be restricted in order to prevent throughput degradation at high loads. This work evaluates, via simulation, three congestion control mechanisms on adaptive cut-through torus networks, using two different deadlock-avoidance methods, under various synthetic traffic patterns. Workload is generated using bursts of data exchanges (instead of a Bernoulli process) to reflect the synchronized nature of data interchanges in parallel applications. Results show that large networks perform their best when most network resources are dedicated to in-transit traffic. Besides, local congestion-control mechanisms are nearly as effective as the more costly global ones for both uniform and nonuniform traffic patterns.

High-performance adaptive routing for networks with arbitrary topology

The Midimew network is an excellent contender for implementing the communication subsystem of a high performance computer. This network is an optimal 2D topology in the sense there are no other symmetric direct networks of degree 4 with a lower average distance or diameter. In fact, it reduces the diameter of the well known torus network by approximately □2. Although the topology was proposed and analyzed a decade ago, the lack of simple deadlock avoidance mechanisms prevented its utilization up to date. This study solved this drawback by applying the Bubble switching mechanism, a low cost deadlock-avoidance strategy developed by the authors. Moreover, by using routing tables we can configure our Virtual Cut-Through adaptive router to implement either a torus or a Midimew network. Thus, we can exploit the topological advantages of Midimew networks by simply changing the disposition of the wrap-around connections of its torus counterpart, without increasing the network implementation cost. To prove this assertion, we have carried out a thorough evaluation, from the hardware cost of the router to the parallel system performance under real loads.

On the design of a high-performance adaptive router for CC-NUMA multiprocessors

The class of dense circulant graphs of degree four with optimal distance-related properties is analyzed in this paper. An algebraic study of this class is done. Two geometric characterizations are given, one in the plane and other in the space. Both characterizations facilitate the analysis of their topological properties and corroborate their suitability for implementing interconnection networks for distributed and parallel computers. Also a distance-hereditary non-disjoint decomposition of these graphs into rings is computed. Besides its practical consequences, this decomposition allows us the presentation of these optimal circulant graphs as a particular evolution of the traditional ring topology.