Forward Checking with Backmarking
نویسنده
چکیده
The forward checking routine (FC) of Haralick and Elliott attempts to encourage early failures within the search tree of constraint satisfaction problems, leading to a reduction in nodes visited, which tends to result in reduced search eeort. In contrast, Gaschnig's backmarking routine (BM) attempts to avoid performing redundant consistency checks. These two algorithms are combined to give us FC-BM, an algorithm that attempts to minimise the number of nodes visited, while avoiding redundant consistency checks. This algorithm is further enhanced such that it incorporates connict-directed backjumping (CBJ) to give us FC-BM-CBJ. A series of experiments are then carried out on really hard problems in an attempt to position these new algorithms with respect to the known algorithms.
منابع مشابه
On the Forward Checking Algorithm
The forward checking algorithm for solving constraint satisfaction problems is a popular and successful alternative to backtracking. However, its success has largely been determined empirically, and there has been limited work towards a real understanding of why and when forward checking is the superior approach. This paper advances our understanding by showing that forward checking is closely ...
متن کاملMinimal Forward Checking with Backmarking
The idea behind forward checking is to check forward so that a wrong decision can be detected in early stage during search and thus futile search space can be pruned. However constraint propagation in forward checking may be overdone in certain situations. In this paper we suggest a way to delay constraint evaluation in forward checking with backmarking. Conflict-directed backtracking can also ...
متن کاملHybrid Algorithms for the Constraint Satisfaction Problem
It might be said that there are five basic tree search algorithms for the constraint satisfaction problem (csp), namely, naive backtracking (BT), backjumping (BJ), conflict-directed backjumping (CBJ), backmarking (BM), and forward checking (FC). In broad terms, BT, BJ, and CBJ describe different styles of backward move (backtracking), whereas BT, BM, and FC describe different styles of forward ...
متن کاملMinimal Forward Checking
Forward Checking is a highly regarded search method used to solve Constraint Satisfaction Problems. This method performs a limited type of lookahead attempting to nd a failure earlier during a backtracking search. In this paper a new search method, Minimal Forward Checking, is introduced which under certain conditions performs the same amount of constraint checking in the worst case as Forward ...
متن کاملBacktracking Algorithms for Constraint Satisfaction Problems { a Tutorial Survey
Over the past twenty years a number of backtracking algorithms for constraint satisfaction problems have been developed. This survey describes the basic backtrack search within the search space framework and then presents a number of improvements including look-back methods such as backjumping, constraint recording, backmarking, and look-ahead methods such as forward checking and dynamic variab...
متن کاملBacktracking Algorithms for Constraint Satisfaction Problems { a Survey
Over the past twenty years, a number of backtracking algorithms for constraint satisfaction problems, have been developed. This survey describes the basic backtrack search within the search space framework and then presents a number of improvements including look-back methods such as backjumping, constraint recording, backmarking, and look-ahead methods such as, forward checking, and dynamic va...
متن کامل