Research in automated planning typically focuses on the development of new or improved algorithms. Yet, an equally important but often overlooked topic is that of how to actually implement these algorithms eciently. In this study, we are making an attempt to close this gap in the context of optimal Markov Decision Process (MDP) planning. Precisely, we present a novel cache-ecient memory representation of MDPs, which we call CSR-MDP, that takes advantage of low-level hardware features such as memory hierarchy. We evaluate the speed improvement provided by our memory representation by comparing the performance of CSR-MDP with the performance obtained by traditional MDP representation. We show that by using our CSR-MDP memory representation, existing MDP solvers, including VI, LRTDP and TVI, are able to nd an optimal policy an order of magnitude faster.
This paper introduces an optimal algorithm for solving the discrete grid-based coverage path planning (CPP) problem. This problem consists in finding a path that covers a given region completely. First, we propose a CPP-solving baseline algorithm based on the iterative deepening depth-first search (ID-DFS) approach. Then, we introduce two branch-and-bound strategies (Loop detection and an Admissible heuristic function) to improve the results of our baseline algorithm. We evaluate the performance of our planner using six types of benchmark grids considered in this study: Coast-like, Random links, Random walk, Simple-shapes, Labyrinth and Wide-Labyrinth grids. We are first to consider these types of grids in the context of CPP. All of them find their practical applications in real-world CPP problems from a variety of fields. The obtained results suggest that the proposed branch-and-bound algorithm solves the problem optimally (i.e., the exact solution is found in each case) orders of magnitude faster than an exhaustive search CPP planner. To the best of our knowledge, no general CPP-solving exact algorithms, apart from an exhaustive search planner, have been proposed in the literature.
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