37036367
A New Routing Algorithm for Cyclic Shifts on BRGC Hypercubes
The hypercube is one of the most efficient networks for parallel computation. It can efficiently simulate any other network of the same size. In particular, the N-node hypercube can simulate any O(N)-node array, binary tree, or mesh of trees with only a small constant factor slowdown [3]. Furthermore, it is completely symmetric and decomposable into sub-hypercubes. These properties, in addition to its simplicity, make it be an excellent and popular architecture for distributed memory parallel computers. Arrays are natural (data or process) structures for many applications. They can be embedded onto hypercube nodes either in natural order or in Binary-Reflected Gray Code (BRGC) order. It has been noted [2] that many algorithms use the cyclic shift (or rotation) in a natural way as a primitive step. Hence, efficient implementation of cyclic shifts on hypercube network is vita1 to the performance of hypercube computers. Cyclic shift algorithms for the natural order embedding have been studied in [51 and those for the BRGC embedding have been studied in [2,4]. The BRGC embedding has the property that any two adjacent numbers are mapped to neighboring nodes that can communicate directly through a link. Therefore, it uses only one link to route a message from any node to its sink node when the shift distance is one. In this case, it is superior to the natural order embedding. The existing cyclic shift algorithms for the BRGC embedding usually route a message by correcting successive bits that differ in source and sink nodes from the less significant end to the more significant end or in the other order with some exceptions. However, all the algorithms have their drawbacks. For example, the two algorithms presented by Johnsson [2] are neither link-disjoint. Thus, two routing paths will contend for the same link. This not only implies the need for local buffering to route the conflicting messages but also leads to the slowdown of the performance. The best disjoint link algorithm in the literature is the one proposed by Ouyang and Palem [4], which in the worst case uses $fi links to route a message from any node to its cyclic shifted sink node on an n-dimensional BRGC hypercube. There also have been many researches on the problem of general permutation routing [ll, but their algorithms are all asymptotically efficient and are not suitable for the cyclic shift problem. In this paper, we propose a new routing algorithm for cyclic shifts on BRGC hypercubes based on the divide-and-conquer approach instead of the usual one. It uses at most IZ links to route a message from any node to its cyclic shifted sink node on an n-dimensional BRGC hypercube and
22896034
Compiler Techniques for Extracting Loop-Level Parallelism
34505121
Adaptive Path-Based Multicast on Wormhole-Routed Hypercubes
In this paper, we consider path-based multicast on wormhole-routed hypercubes. A minimum set of routing restrictions is used as the base routing algorithm. To correctly perform multicast, we present the natural list to sort the destination nodes. It can be proved to be deadlock-free for both one-port and multi-port systems. Furthermore, it creates only one worm for each multicast. Between each pair of nodes in a multicast path with distance k, on the average, there are at least (k+1)!/2k adaptive shortest paths, which is superior to previous works. We also propose a heuristic algorithm to reduce the path length. The simulation result shows that its sustainable throughput is much better than related works. In addition, unicast and broadcast can be treated as degenerated cases and use the same routing algorithm. Therefore, it offers a comprehensive routing solution for communication on hypercubes.
1928330
A near-optimal broadcasting algorithm in all-port wormhole-routed hypercubes
For massively parallel computing mechanism, broadcasting is widely used in a variety of applications. When the computation is distributed among the powerful processors, communication overhead always limits the speedup. To reduce the influence of communication latency, a variety of routing methods have been discussed. In this paper, we propose an efficient routing method of broadcasting on all-port worrnhole-routed hybercubes. By exploiting the distance-insensitivity of wormhole switching, this efficient broadcasting algorithm reduce communication latency to l_rzl_logz(n+l )11steps in an n-dimensional hypercube, which is much better than previous results and very close to the theoretical optimum, [rz/log2(n+l )1.Further, by adopting the Hamming code, a well-known algebraic approach in coding theory, this proposed algorithm is contention-free in each broadcasting step.
31866645
Optimal Processor Mapping for Linear-Complement Communication on Hypercubes
In this paper, we address the problem of minimizing channel contention of linear-complement communication on wormhole-routed hypercubes. Our research reveals that, for traditional routing algorithms, the degree of channel contention of a linear-complement communication can be quite large. To solve this problem, we propose an alternative approach, which applies processor reordering mapping at compile time. In this compiler approach, processors are logically reordered according to the given communication(s) so that the new communication(s) can be efficiently realized on the hypercube network. It is proved that, for any linear-complement communication, there exists a reordering mapping such that the new communication has minimum channel contention. An O(n/sup 3/) algorithm is proposed to find such a mapping for an n-dimensional hypercube. An algorithm based on dynamic programming is also proposed to find an optimal reordering mapping for a set of linear-complement communications. Several computer simulations have been conducted and the results clearly show the advantage of the proposed approach.
14558760
A Constrained Clustering Approach to Duplicate Detection Among Relational Data
This paper proposes an approach to detect duplicates among relational data. Traditional methods for record linkage or duplicate detection work on a set of records which have no explicit relations with each other. These records can be formatted into a single database table for processing. However, there are situations that records from different sources can not be flattened into one table and records within one source have certain (semantic) relations between them. The duplicate detection issue of these relational data records/instances can be dealt with by formatting them into several tables and applying traditional methods to each table. However, as the relations among the original data records are ignored, this approach generates poor or inconsistent results. This paper analyzes the characteristics of relational data and proposes a particular clustering approach to perform duplicate detection. This approach incorporates constraint rules derived from the characteristics of relational data and therefore yields better and more consistent results, which are revealed by our experiments.
5531222
Divide and Compose: SCC Refinement for Language Emptiness
We propose a refinement approach to symbolic SCC analysis, which performs large parts of the computation on abstracted systems, and on small subsets of the state space. For language-emptiness checking, it quickly discards uninteresting parts of the state space; for the remaining states, it adapts the model checking computation to the strength of the SCCs at hand. 
 
We present a general framework for SCC refinement, which uses a compositional approach to generate and refine overapproximations. We show that our algorithm significantly outperforms the one of Emerson and Lei.
14633874
Multi-platform Soccer Robot Development System
Robot soccer is a challenging research domain, which involves multiple agents (physical robots or "softbots") to work together in a dynamic, noisy, cooperative and adversarial environment to achieve specific objectives. The paper focuses on the design and implementation of an effective system for developing a small-size physical soccer team for the competition of RoboCup. There are three goals preset in our research, that is, robust individual behaviors, controllable cooperation and behavioral learning. The system is therefore required to collect data in real-time situations and repeat experiments accurately, which are found difficult to be achieved in pure physical or simulated case. A distinct feature of our system is that it is a close combination of three functional parts: physical test platform, simulation platform and measurement platform, which support each other to overcome many defects inherent in traditional physical system or simulation system.
586755
Mixed symbolic representations for model checking software programs
We present an efficient symbolic search algorithm for software model checking. The algorithm combines multiple symbolic representations to efficiently represent the transition relation and reachable states and uses a combination of decision procedures for Boolean and integer representations. Our main contributions include: (1) mixed symbolic representations to model C programs with rich data types and complex expressions; and (2) new symbolic search strategies and optimization techniques specific to sequential programs that can significantly improve the scalability of model checking algorithms. Our controlled experiments on real-world software programs show that the new symbolic search algorithm can achieve several orders-of-magnitude improvements over existing methods. The proposed techniques are extremely competitive in handling sequential models of non-trivial sizes, and also compare favorably to popular Boolean-level model checking algorithms based on BDDs and SAT
2969808
Improving Ariadne's Bundle by Following Multiple Threads in Abstraction Refinement
The authors propose a scalable abstraction-refinement method for model checking invariant properties on large sequential circuits, which is based on fine-grain abstraction and simultaneous analysis of all abstract counterexamples of the shortest length. Abstraction efficiency is introduced to measure for a given abstraction-refinement algorithm how much of the concrete model is required to make the decision. The fully automatic techniques presented in this paper can efficiently reach or come near to the maximal abstraction efficiency. First, a fine-grain abstraction approach is given to keep the abstraction granularity small by breaking down large combinational logic cones with Boolean network variables (BNVs) and then treating both state variables and BNVs as atoms in abstraction. Second, a refinement algorithm is proposed based on an improved Ariadne's bundle In the legend of Theseus, Ariadne's bundle contained one ball of thread to help Theseus navigate the labyrinth. In this paper, we work with multiple threads-hence, the "improved." of synchronous onion rings on the abstract model, through which the transitions contain all shortest abstract counterexamples. The synchronous onion rings are exploited in two distinct ways to provide global guidance to the abstraction refinement process. The scalability of our algorithm is ensured in the sense that all the analysis and computation required in our refinement algorithm are conducted on the abstract model. Finally, we derive sequential don't cares from the invisible variables and use them to constrain the behavior of the abstract model. We conducted experimental comparisons of our new method with various existing techniques. The results show that our method outperforms other counterexample-guided methods in terms of both run time and abstraction efficiency