Evgeny Mishlyakov, Mikhail Gruntov, Alexander Shleyfman, E. Karpas
{"title":"A Deterministic Search Approach for Solving Stochastic Drone Search and Rescue Planning Without Communications","authors":"Evgeny Mishlyakov, Mikhail Gruntov, Alexander Shleyfman, E. Karpas","doi":"10.1609/socs.v17i1.31544","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31544","url":null,"abstract":"In disaster relief efforts, delivering aid to areas with no communication poses a significant challenge. Unmanned aerial vehicles (UAVs) can be utilized to deliver aid kits to survivors in hard-to-reach areas; unfortunately, in some areas, lack of communication and infrastructure presents a key problem. \u0000In this paper, we address a stochastic planning problem of planning for a set of UAVs that deliver aid kits to areas that lack communications, where we do not know in advance the locations where aid kits need to be delivered, but rather have probabilistic information about the locations of aid targets.\u0000Our main insight is that, despite the stochastic nature of this problem, we can solve it through deterministic search by monitoring the expected reward for each partial solution. This insight enables the application of deterministic planning techniques, empirically demonstrating a notable improvement in efficiency and response speed. Our approach presents a promising solution to addressing the challenge of delivering aid in regions with limited radio infrastructure, as well as similar planning problems.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"51 24","pages":"73-81"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sean Mariasin, Andrew Coles, E. Karpas, Wheeler Ruml, S. E. Shimony, Shahaf S. Shperberg
{"title":"Evaluating Distributional Predictions of Search Time: Put Up or Shut Up Games (Extended Abstract)","authors":"Sean Mariasin, Andrew Coles, E. Karpas, Wheeler Ruml, S. E. Shimony, Shahaf S. Shperberg","doi":"10.1609/socs.v17i1.31579","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31579","url":null,"abstract":"Metareasoning can be a helpful technique for controlling search in situations where computation time is an important resource, such as \u0000real-time planning and search, algorithm portfolios, and concurrent planning and execution. Metareasoning often involves an estimate of the remaining search time of a running algorithm, and several ways to compute such estimates have been presented in the literature. In this paper, we argue that many applications actually require a full estimated probability distribution over the remaining time, rather than just a point estimate of expected search time. We study several methods for estimating such distributions, including some novel adaptations of existing schemes.\u0000To properly evaluate the estimates, we introduce `put-up or shut-up games', which probe the distributional estimates without requiring infeasible computation.\u0000Our experimental evaluation reveals that estimates that are more accurate in expected value do not necessarily deliver better distributions, yielding worse scores in the game.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"30 4","pages":"277-278"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141274347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Neural Sequence Generation with Constraints via Beam Search with Cuts: A Case Study on VRP","authors":"Pouya Shati, Eldan Cohen, Sheila A. McIlraith","doi":"10.1609/socs.v17i1.31549","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31549","url":null,"abstract":"In recent years, neural sequence models have been applied successfully to solve combinatorial optimization problems. Solutions, encoded as sequences, are typically generated from trained models via beam search, a search algorithm that generates sequences token-by-token while keeping a fixed number of promising partial solutions at each step. In this paper, we explore the problem of augmenting beam search generation with the enforcement of requirements---hard constraints that any generated solution must adhere to. We propose a hybrid approach, by encoding the requirements in the form of a constraint satisfaction problem (CSP) and iteratively solving the CSP to cut any partial solution within the beam search that is incapable of satisfying the requirements. We study this problem in the context of vehicle routing problems (VRP) further augmented with capacity-related or temporal requirements. We experimentally show that cuts often allow us to satisfy the requirements with negligible impact on solution quality. Without the use of cuts, beam search is shown to be exponentially less likely to satisfy the requirements as the length of the solution increases and/or the requirements are strengthened.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"5 11","pages":"118-126"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pablo Araneda, Carlos Hernández Ulloa, Nicolás Rivera, Jorge A. Baier
{"title":"Finding a Small, Diverse Subset of the Pareto Solution Set in Bi-Objective Search (Extended Abstract)","authors":"Pablo Araneda, Carlos Hernández Ulloa, Nicolás Rivera, Jorge A. Baier","doi":"10.1609/socs.v17i1.31568","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31568","url":null,"abstract":"Bi-objective search requires computing a Pareto solution set which contains a set of paths. In real-world applications, Pareto solution sets may contain several tens or even hundreds of solutions. For a human user trying to commit to just one of these paths, navigating through a large solution set may become overwhelming, which motivates the problem of computing small, good-quality subsets of Pareto frontiers. This document presents two main contributions. First, we provide a simple formalization of good-quality subsets of a Pareto solution set. For this, we use measure of richness which has been employed in the study of Population Dynamics. Second, we propose Chebyshev BOA*, a variant of BOA*\u0000 to compute good-quality subset approximations.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"77 10","pages":"255-256"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141280897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Han Zhang, Oren Salzman, Ariel Felner, Carlos Hernández Ulloa, Sven Koenig
{"title":"A-A*pex: Efficient Anytime Approximate Multi-Objective Search","authors":"Han Zhang, Oren Salzman, Ariel Felner, Carlos Hernández Ulloa, Sven Koenig","doi":"10.1609/socs.v17i1.31556","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31556","url":null,"abstract":"In the multi-objective search problem, a typical task is to compute the Pareto frontier, i.e., the set of all undominated solutions. However, computing the entire Pareto frontier can be very time-consuming, and in practice, we often have limited deliberation time. Therefore, this paper focuses on solving the multi-objective search problem with anytime algorithms, which compute an initial approximate frontier quickly and then work to find more solutions until eventually finding the entire Pareto frontier. Existing work has investigated such anytime algorithms for problem instances with only two objectives. In this paper, we propose Anytime A*pex (A-A*pex), which works with any number of objectives. In each iteration of A-A*pex, it runs A*pex, a state-of-the-art approximate multi-objective search algorithm, to compute more solutions. From one iteration to the next, A-A*pex can either reuse its previous search effort or restart from scratch. Our experimental results show that an A-A*pex variant that mixes\u0000reusing its search effort and restarting from scratch yields the best runtime performance. We also show that A-A*pex often computes solutions that collectively approximate the Pareto frontier much better than the solutions found by state-of-the-art multi-objective search algorithms for short deliberation times.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"37 2","pages":"179-187"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141274141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Finiding All Optimal Solutions in Multi-Agent Path Finding (Extended Abstract)","authors":"Shahar Bardugo, Dor Atzmon","doi":"10.1609/socs.v17i1.31570","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31570","url":null,"abstract":"The Multi-Agent Path Finding problem (MAPF) aims to find conflict-free paths for a group of agents leading each agent to its respective goal. In this paper, we study the requirement of finding all optimal solutions in MAPF. We discuss the representation of all optimal solutions, propose three algorithms for finding them, and compare the algorithms experimentally.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"38 11","pages":"259-260"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141278792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yue Zhang, Zhe Chen, Daniel D. Harabor, P. L. Bodic, P. Stuckey
{"title":"Planning and Exection in Multi-Agent Path Finding: Models and Algorithms (Extended Abstract)","authors":"Yue Zhang, Zhe Chen, Daniel D. Harabor, P. L. Bodic, P. Stuckey","doi":"10.1609/socs.v17i1.31592","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31592","url":null,"abstract":"In applications of Multi-Agent Path Finding (MAPF), it is often the sum of planning and execution times that needs to be minimised (i.e., the Goal Achievement Time). Yet current methods seldom optimise for this objective. Optimal algorithms reduce execution time, but may require exponential planning time. Non-optimal algorithms reduce planning time, but at the expense of increased path length. To address these limitations we introduce PIE (Planning and Improving while Executing), a new framework for concurrent planning and execution in MAPF. We first show how PIE for one-shot MAPF improves practical performance compared to sequential planning and execution.We then adapt PIE to Lifelong MAPF, a popular application setting where agents are continuously assigned new goals and where additional decisions are required to ensure feasibility. We examine a variety of different approaches to overcome these challenges and we conduct comparative experiments vs. recently proposed alternatives. Results show that PIE substantially outperforms existing methods for One-shot and Lifelong MAPF.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"29 12","pages":"303-304"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141275513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Solving Facility Location Problems via FastMap and Locality Sensitive Hashing","authors":"Ang Li, P. Stuckey, Sven Koenig, T. K. S. Kumar","doi":"10.1609/socs.v17i1.31541","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31541","url":null,"abstract":"Facility Location Problems (FLPs) arise while serving multiple customers in a shared environment, minimizing transportation and other costs. Hence, they involve the optimal placement of facilities. They are defined on graphs as well as in Euclidean spaces with or without obstacles; and they are typically NP-hard to solve optimally. There are many heuristic algorithms tailored to different kinds of FLPs. However, FLPs defined in Euclidean spaces without obstacles are the most amenable to efficient and effective heuristic algorithms. This motivates the idea of quickly reformulating FLPs on graphs and in Euclidean spaces with obstacles to FLPs in Euclidean spaces without obstacles. Towards this end, we propose a new approach that uses FastMap and Locality Sensitive Hashing. FastMap is a near-linear-time algorithm that embeds the vertices of a graph in a Euclidean space while approximately preserving graph-based distances as Euclidean distances for all pairs of vertices. Through extensive experiments, we show that our approach significantly outperforms other state-of-the-art competing algorithms on a variety of FLPs: the Multi-Agent Meeting, Vertex K-Median (VKM), Weighted VKM, and the Capacitated VKM problems.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"13 1","pages":"46-54"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141279657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Parallelizing Multi-objective A* Search (Extended Abstract)","authors":"Saman Ahmadi","doi":"10.1609/socs.v17i1.31567","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31567","url":null,"abstract":"The Multi-objective Shortest Path (MOSP) problem aims to find all Pareto-optimal paths between two points in a graph with multiple edge costs. Recent studies on multi-objective search with A* have demonstrated superior performance in solving difficult MOSP instances. This paper proposes a novel parallel multi-objective search framework that can accelerate recent A*-based solutions by several factors.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"55 1","pages":"253-254"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141280977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Clemens Büchner, Remo Christen, Salomé Eriksson, Thomas Keller
{"title":"Hitting Set Heuristics for Overlapping Landmarks in Satisficing Planning","authors":"Clemens Büchner, Remo Christen, Salomé Eriksson, Thomas Keller","doi":"10.1609/socs.v17i1.31558","DOIUrl":"https://doi.org/10.1609/socs.v17i1.31558","url":null,"abstract":"Landmarks are a core component of LAMA, a state-of-the-art satisficing planning\u0000system based on heuristic search. It uses landmarks to estimate the goal\u0000distance by summing up the costs of their cheapest achievers. This procedure\u0000ignores synergies between different landmarks: The cost of an action is\u0000counted multiple times if it is the cheapest achiever of several landmarks.\u0000Common admissible landmark heuristics tackle this problem by\u0000underapproximating the cost of a minimum hitting set of the landmark\u0000achievers. We suggest to overapproximate it by computing suboptimal hitting\u0000sets instead if admissibility is not a requirement. As our heuristics consider\u0000synergies between landmarks, we further propose to relax certain restrictions\u0000LAMA imposes on the number of landmarks and synergies between them. Our\u0000experimental evaluation shows a reasonable increase in the number of\u0000landmarks that leads to better guidance when used with our new heuristics.","PeriodicalId":425645,"journal":{"name":"Symposium on Combinatorial Search","volume":"25 2","pages":"198-202"},"PeriodicalIF":0.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141274188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}