Date

2018-06-29

Author

Arslan, Hilal
Manguoğlu, Murat

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Solving the shortest path problem on large scale networks is crucial for many applications. As parallelism became more common with the advent of multi-core architectures as well as large and complex networks have begun to emerge in many settings, it is inevitable to come up with algorithms that take advantage of the current architectures. One alternative to solve the shortest path problem is to use one of the classical or improved parallel variations of the Dijkstra’s algorithm. However, when the size of the network becomes large, finding the shortest path requires excessive computational time. Recently, some bio-inspired methods to find the shortest path have been proposed, such as Genetic algorithms, Ant Colony Optimization, Swarm Systems, and Physarum Solver. Physarum Solver is capable of finding the shortest path in a labyrinth and is developed by modelling the behavior of Physarum Polycephalum, which is an amoeba-like organism. Physarum Solver has been applied in many applications recently. It can efficiently solve a variety of network optimization problems such as the traveling salesmen problem, the vehicle routing problem, and scheduling of multi-gravity assist trajectories and various optimization problems required linear programming. However, earlier studies provide only sequential variants of Physarum Solver. In this study, a parallel and scalable Physarum Solver is proposed with the objective to find the shortest path for static graphs with positive edge weights. The proposed scheme is applied on both large scale realistic and real world static graphs as well as dynamically changing graphs. Physarum Solver requires the solution of the linear systems whose coefficient matrix is an M-matrix at each iteration. This step is the most time consuming step especially for problems having excessive data or information size. However, Physarum related studies in the literature do not take advantage of M-matrix property of the coefficient matrix to solve the linear systems in Physarum Solver. They use a direct method to solve such systems, which is infeasible for large scale problems with several millions of unknowns. A parallel preconditioned iterative method for solving prementioned sparse linear systems is presented. The proposed preconditioner is specifically designed based on the properties of the coefficient matrix of those linear systems, and the effectiveness of the proposed preconditioner is compared against other state-of-the-art preconditioners on dynamic graphs. Furthermore, the proposed dynamic algorithm is designed to be suitable for dynamically changing graphs since it uses the information arising in earlier iterations. The parallel scalability as well as the effect of changing the edge weights to the time to solution are evaluated for each graph model, separately and compared against a state-of-the-art parallel implementation of the Dijkstra’s algorithm on a parallel multicore cluster. In contrast to the classical shortest path algorithms, the proposed scheme has a distinct advantage that it is using array based data-structures and optimized kernels which take advantage of today’s multi level cache hierarchies. Our implementation exhibits remarkable speedups with comparable accuracy for synthetic and real-world applications.

URI

https://pmaa18.inf.ethz.ch/dynamic/schedule.html
https://hdl.handle.net/11511/75798

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Department of Computer Engineering, Conference / Seminar