Weixiong Zhang | Washington University in St. Louis (original) (raw)
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Papers by Weixiong Zhang
Artificial Intelligence, 1994
Artificial Intelligence, 1996
Distributed breakout algorithm (DBA) is an effi- cient method for solving distributed constraint ... more Distributed breakout algorithm (DBA) is an effi- cient method for solving distributed constraint sat- isfaction problems (CSP). Inspired by its potential of being an efficient, low-overhead agent coordi- nation method for problems in distributed sensor networks, we study DBA' s properties in this paper. We specifically show that on an acyclic graph of nodes, DBA can find a solution in
PLOS Computational Biology, 2007
Artificial Intelligence, 2005
It is well known that the Davis-Putnam-Logemann-Loveland (DPLL) algorithm for satisfiability (SAT... more It is well known that the Davis-Putnam-Logemann-Loveland (DPLL) algorithm for satisfiability (SAT) can be extended to an algorithm for maximum SAT (max-SAT). In this paper, we propose a number of strategies to significantly improve this max-SAT method. The first strategy is a set of unit propagation rules; the second is an effective lookahead heuristic based on linear programming; and the third strategy is a dynamic variable ordering that exploits problem constrainedness during search. We integrate these strategies in an efficient complete solver for both max-SAT and weighted max-SAT. Our experimental results on random problem instances and many instances from SATLIB demonstrate the efficacy of these strategies and show that the new solver is able to significantly outperform most of the existing complete max-SAT solvers, with a few orders of magnitude of improvement in running time in many cases.
Artificial Intelligence, 2005
... We experimentally show that DSA has a phase-transition or threshold behavior, in that its sol... more ... We experimentally show that DSA has a phase-transition or threshold behavior, in that its solution quality degenerates abruptly and dramatically when the degree of parallel executions of distributed agents increases beyond some critical value. ...
In this and the following chapter, we consider what approaches one should take when one is confro... more In this and the following chapter, we consider what approaches one should take when one is confronted with a real-world application of the TSP. What algorithms should be used under which circumstances? We are in particular interested in the case where instances are too large for optimization to be feasible. Here theoretical results can be a useful initial guide, but the most valuable information will likely come from testing implementations of the heuristics on test beds of relevant instances. This chapter considers the symmetric TSP; the next considers the more general and less well-studied asymmetric case.
The purpose of this paper is to provide a preliminary report on the first broad-based experimenta... more The purpose of this paper is to provide a preliminary report on the first broad-based experimental comparison of modern heuristics for the asymmetric traveling salesmen problem (ATSP). There are currently three general classes of such heuristics: classical tour construction heuristics such as Nearest Neighbor and the Greedy algorithm, local search algorithms based on re-arranging segments of the tour, as exemplified by the Kanellakis-Papadimitriou algorithm [KP80], and algorithms based on patching together the cycles in a minimum cycle cover, the best of which are variants on an algorithm proposed by Zhang [Zha93]. We test implementations of the main contenders from each class on a variety of instance types, introducing a variety of new random instance generators modeled on real-world applications of the ATSP. Among the many tentative conclusions we reach is that no single algorithm is dominant over all instance classes, although for each class the best tours are found either by Zhang’s algorithm or an iterated variant on Kanellakis-Papadimitriou.
Artificial Intelligence, 1995
... acknowledge helpful discussions with Richard Karp, David Johnson, Donald Miller, Joseph Pekny... more ... acknowledge helpful discussions with Richard Karp, David Johnson, Donald Miller, Joseph Pekny and Bruno Repetto, comments from David John-son ... 3] Carpaneto, G., and P. Toth, \Some new branch-ing and bounding criteria for the asymmetric trav-eling salesman problem ...
Artificial Intelligence, 1996
Artificial Intelligence, 1994
Artificial Intelligence, 1996
Distributed breakout algorithm (DBA) is an effi- cient method for solving distributed constraint ... more Distributed breakout algorithm (DBA) is an effi- cient method for solving distributed constraint sat- isfaction problems (CSP). Inspired by its potential of being an efficient, low-overhead agent coordi- nation method for problems in distributed sensor networks, we study DBA' s properties in this paper. We specifically show that on an acyclic graph of nodes, DBA can find a solution in
PLOS Computational Biology, 2007
Artificial Intelligence, 2005
It is well known that the Davis-Putnam-Logemann-Loveland (DPLL) algorithm for satisfiability (SAT... more It is well known that the Davis-Putnam-Logemann-Loveland (DPLL) algorithm for satisfiability (SAT) can be extended to an algorithm for maximum SAT (max-SAT). In this paper, we propose a number of strategies to significantly improve this max-SAT method. The first strategy is a set of unit propagation rules; the second is an effective lookahead heuristic based on linear programming; and the third strategy is a dynamic variable ordering that exploits problem constrainedness during search. We integrate these strategies in an efficient complete solver for both max-SAT and weighted max-SAT. Our experimental results on random problem instances and many instances from SATLIB demonstrate the efficacy of these strategies and show that the new solver is able to significantly outperform most of the existing complete max-SAT solvers, with a few orders of magnitude of improvement in running time in many cases.
Artificial Intelligence, 2005
... We experimentally show that DSA has a phase-transition or threshold behavior, in that its sol... more ... We experimentally show that DSA has a phase-transition or threshold behavior, in that its solution quality degenerates abruptly and dramatically when the degree of parallel executions of distributed agents increases beyond some critical value. ...
In this and the following chapter, we consider what approaches one should take when one is confro... more In this and the following chapter, we consider what approaches one should take when one is confronted with a real-world application of the TSP. What algorithms should be used under which circumstances? We are in particular interested in the case where instances are too large for optimization to be feasible. Here theoretical results can be a useful initial guide, but the most valuable information will likely come from testing implementations of the heuristics on test beds of relevant instances. This chapter considers the symmetric TSP; the next considers the more general and less well-studied asymmetric case.
The purpose of this paper is to provide a preliminary report on the first broad-based experimenta... more The purpose of this paper is to provide a preliminary report on the first broad-based experimental comparison of modern heuristics for the asymmetric traveling salesmen problem (ATSP). There are currently three general classes of such heuristics: classical tour construction heuristics such as Nearest Neighbor and the Greedy algorithm, local search algorithms based on re-arranging segments of the tour, as exemplified by the Kanellakis-Papadimitriou algorithm [KP80], and algorithms based on patching together the cycles in a minimum cycle cover, the best of which are variants on an algorithm proposed by Zhang [Zha93]. We test implementations of the main contenders from each class on a variety of instance types, introducing a variety of new random instance generators modeled on real-world applications of the ATSP. Among the many tentative conclusions we reach is that no single algorithm is dominant over all instance classes, although for each class the best tours are found either by Zhang’s algorithm or an iterated variant on Kanellakis-Papadimitriou.
Artificial Intelligence, 1995
... acknowledge helpful discussions with Richard Karp, David Johnson, Donald Miller, Joseph Pekny... more ... acknowledge helpful discussions with Richard Karp, David Johnson, Donald Miller, Joseph Pekny and Bruno Repetto, comments from David John-son ... 3] Carpaneto, G., and P. Toth, \Some new branch-ing and bounding criteria for the asymmetric trav-eling salesman problem ...
Artificial Intelligence, 1996