New Fault Tolerant Multicast Routing Techniques to Enhance Distributed-Memory Systems Performance

Distributed-memory systems are a key to achieve high performance computing and the most favorable architectures used in advanced research problems. Mesh connected multicomputer are one of the most popular architectures that have been implemented in many distributed-memory systems. These systems must support communication operations efficiently to achieve good performance. The wormhole switching technique has been widely used in design of distributed-memory systems in which the packet is divided into small flits. Also, the multicast communication has been widely used in distributed-memory systems which is one source node sends the same message to several destination nodes. Fault tolerance refers to the ability of the system to operate correctly in the presence of faults. Development of fault tolerant multicast routing algorithms in 2D mesh networks is an important issue. This dissertation presents, new fault tolerant multicast routing algorithms for distributed-memory systems performance using wormhole routed 2D mesh. These algorithms are described for fault tolerant routing in 2D mesh networks, but it can also be extended to other topologies. These algorithms are a combination of a unicast-based multicast algorithm and tree-based multicast algorithms. These algorithms works effectively for the most commonly encountered faults in mesh networks, f-rings, f-chains and concave fault regions. It is shown that the proposed routing algorithms are effective even in the presence of a large number of fault regions and large size of fault region. These algorithms are proved to be deadlock-free. Also, the problem of fault regions overlap is solved. Four essential performance metrics in mesh networks will be considered and calculated; also these algorithms are a limited-global-information-based multicasting which is a compromise of local-information-based approach and global-information-based approach. Data mining is used to validate the results and to enlarge the sample. The proposed new multicast routing techniques are used to enhance the performance of distributed-memory systems. Simulation results are presented to demonstrate the efficiency of the proposed algorithms

A fault-tolerant routing strategy for k-ary n-direct s-indirect topologies based on intermediate nodes

[EN] Exascale computing systems are being built with thousands of nodes. The high number of components of these systems significantly increases the probability of failure. A key component for them is the interconnection network. If failures occur in the interconnection network, they may isolate a large fraction of the machine. For this reason, an efficient fault-tolerant mechanism is needed to keep the system interconnected, even in the presence of faults. A recently proposed topology for these large systems is the hybrid k-ary n-direct s-indirect family that provides optimal performance and connectivity at a reduced hardware cost. This paper presents a fault-tolerant routing methodology for the k-ary n-direct s-indirect topology that degrades performance gracefully in presence of faults and tolerates a large number of faults without disabling any healthy computing node. In order to tolerate network failures, the methodology uses a simple mechanism. For any source-destination pair, if necessary, packets are forwarded to the destination node through a set of intermediate nodes (without being ejected from the network) with the aim of circumventing faults. The evaluation results shows that the proposed methodology tolerates a large number of faults. For instance, it is able to tolerate more than 99.5% of fault combinations when there are 10 faults in a 3-D network with 1000 nodes using only 1 intermediate node and more than 99.98% if 2 intermediate nodes are used. Furthermore, the methodology offers a gracious performance degradation. As an example, performance degrades only by 1% for a 2-D network with 1024 nodes and 1% faulty links.This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO), by FEDER funds under Grant TIN2015-66972-C5-1-R, by Programa de Ayudas de Investigación y Desarrollo (PAID) from Universitat Politècnica de alència and by the financial support of the FP7 HiPEAC Network of Excellence under grant agreement 287759Peñaranda Cebrián, R.; Gómez Requena, ME.; López Rodríguez, PJ.; Gran, EG.; Skeie, T. (2017). A fault-tolerant routing strategy for k-ary n-direct s-indirect topologies based on intermediate nodes. Concurrency and Computation Practice and Experience. 29(13):1-11. https://doi.org/10.1002/cpe.4065S111291

Self-stabilizing wormhole routing in hypercubes

Wormhole routing is an efficient technique used to communicate message packets between processors when they are not completely connected. To the best of our knowledge, this is the first attempt at designing a self-stabilizing wormhole routing algorithm for hypercubes. Our first algorithm handles all types of faults except for node/link failures. This algorithm achieves optimality in terms of routing path length by following only the preferred dimensions. In an n-dimensional hypercube, those dimensions in which source and destination address bits differ are called preferred dimensions. Our second algorithm handles topological changes. We propose an efficient scheme of rerouting flits in case of node/link failures. Similar to the first algorithm, this algorithm also tries to follow preferred dimensions if they are nonfaulty at the time of transmitting the flits. However, due to topological faults it is necessary to take non-preferred dimensions resulting in suboptimality of path selection. Formal proof of correctness for both solutions is given. (Abstract shortened by UMI.)

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

More Improvement by Helping Ant to Fault-Tolerant Heuristic Routing Algorithm in Mesh Networks

Abstract: Routing with fault-tolerant mechanisms has a crucial effect on the fast exchange of information in variety of networks including mesh networks. This study attempts to choose an optimal path in terms of fault tolerance to transmit messages from source to destination while taking into account faulty nodes in such mesh networks. In this study, we take advantage of ant colony optimization algorithm to propose Adaptive Heuristic Routing algorithms to this problem. We use color pheromone ants to overcome problem of fail-recover behavior of network components. The proposed method is compared with fault-tolerant routing algorithm in mesh networks using the balanced ring. Simulation results depict that this method reacted quickly in terms of network faults, meanwhile in each time step the data can choose the optimal path to reach their destination. In this study, we improve performance of the proposed method using update ants to inform other nodes about the discovered shortest path. Simulation results show that the proposed method dramaticcaly increase efficiency of routing mechanism in mesh networks

Resilient Routing Implementation in 2D Mesh NoC

With the rapid shrinking of technology and growing integration capacity, the probability of failures in Networks-on-Chip (NoCs) increases and thus, fault tolerance is essential. Moreover, the unpredictable locations of these failures may influence the regularity of the underlying topology, and a regular 2D mesh is likely to become irregular. Thus, for these failure-prone networks, a viable routing framework should comprise a topology-agnostic routing algorithm along with a cost-effective, scalable routing mechanism able to handle failures, irrespective of any particular failure patterns. Existing routing techniques designed to route irregular topologies efficiently lack flexibility (logic-based), scalability (table-based) or relaxed switch design (uLBDR-based). Designing an efficient routing implementation technique to address irregular topologies remains a pressing research problem. To address this, we present a fault resilient routing mechanism for irregular 2D meshes resulting from failures. To handle irregularities, it avoids using routing tables and employs a few fixed configuration bits per switch resulting in a scalable approach. Experiments demonstrate that the proposed approach is guaranteed to tolerate all locations of single and double-link failures and most multiple failures. Also, unlike uLBDR it is not restricted to any particular switching technique and does not replicate any extra messages. Along with fault tolerance, the proposed mechanism can achieve better network performance in fault-free cases. The proposed technique achieves graceful performance degradation during failure. Compared to uLBDR, our method has 14% less area requirements and 16% less overall power consumption