A general analytical model of adaptive wormhole routing in k-ary n-cubes

Several analytical models of fully adaptive routing have recently been proposed for k-ary n-cubes and hypercube networks under the uniform traffic pattern. Although,hypercube is a special case of k-ary n-cubes topology, the modeling approach for hypercube is more accurate than karyn-cubes due to its simpler structure. This paper proposes a general analytical model to predict message latency in wormhole-routed k-ary n-cubes with fully adaptive routing that uses a similar modeling approach to hypercube. The analysis focuses Duato's fully adaptive routing algorithm [12], which is widely accepted as the most general algorithm for achieving adaptivity in wormhole-routed networks while allowing for an efficient router implementation. The proposed model is general enough that it can be used for hypercube and other fully adaptive routing algorithms

The Effect Of Hot Spots On The Performance Of Mesh--Based Networks

Direct network performance is affected by different design parameters which include number of virtual channels, number of ports, routing algorithm, switching technique, deadlock handling technique, packet size, and buffer size. Another factor that affects network performance is the traffic pattern. In this thesis, we study the effect of hotspot traffic on system performance. Specifically, we study the effect of hotspot factor, hotspot number, and hot spot location on the performance of mesh-based networks. Simulations are run on two network topologies, both the mesh and torus. We pay more attention to meshes because they are widely used in commercial machines. Comparisons between oblivious wormhole switching and chaotic packet switching are reported. Overall packet switching proved to be more efficient in terms of throughput when compared to wormhole switching. In the case of uniform random traffic, it is shown that the differences between chaotic and oblivious routing are indistinguishable. Networks with low number of hotspots show better performance. As the number of hotspots increases network latency tends to increase. It is shown that when the hotspot factor increases, performance of packet switching is better than that of wormhole switching. It is also shown that the location of hotspots affects network performance particularly with the oblivious routers since their achieved latencies proved to be more vulnerable to changes in the hotspot location. It is also shown that the smaller the size of the network the earlier network saturation occurs. Further, it is shown that the chaos router’s adaptivity is useful in this case. Finally, for tori, performance is not greatly affected by hotspot presence. This is mostly due to the symmetric nature of tori

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-2015-26080Andújar-Muñoz, FJ.; Villar, JA.; Sanchez Garcia, JL.; Alfaro Cortes, FJ.; Duato Marín, 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

Deadlock-Free Multi-Path Routing for Torus-Based NoCs

In our previous work, a multi-path routing (MPR) scheme was proposed to maximize the data throughput for torus-based NoCs by utilizing multiple paths for concurrent data transmission. In this paper, a deadlock-free virtual channel model is proposed for the MPR scheme. In this virtual channel model, every physical channel on the network is split into about 3.5 virtual channels on average. It is proved that any minimal routing algorithm (including the MPR scheme) using this model is deadlock-free. The MPR scheme employing this new virtual channel model is still a fully adaptive one. The performance of the MPR scheme using the proposed virtual channel model is evaluated through simulations and compared with the fully adaptive single-path minimal routing (SPR) scheme with the same virtual channel model. Simulation results show that MPR achieves better average message latency and normalized accepted traffic than SPR under both uniform and nonuniform traffic in general

A performance model of multicast communication in wormhole-routed networks on-chip

Collective communication operations form a part of overall traffic in most applications running on platforms employing direct interconnection networks. This paper presents a novel analytical model to compute communication latency of multicast as a widely used collective communication operation. The novelty of the model lies in its ability to predict the latency of the multicast communication in wormhole-routed architectures employing asynchronous multi-port routers scheme. The model is applied to the Quarc NoC and its validity is verified by comparing the model predictions against the results obtained from a discrete-event simulator developed using OMNET++