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Given an initial assignment of values to all the variables of a constraint satisfaction problem (with one or more constraints not satisfied), select a variable from the set of variables with conflicts violating one or more of its constraints. Assign to this variable a value that minimizes the number of conflicts (usually breaking ties randomly).
The algorithm works by iteratively assigning free variables, and when the algorithm encounters a bad assignment, then it backtracks to a previous iteration and chooses a different assignment of variables. It relies on a Branching Heuristic to pick the next free variable assignment; the branching algorithm effectively makes choosing the variable ...
In this basic backtracking algorithm, consistency is defined as the satisfaction of all constraints whose variables are all assigned. Several variants of backtracking exist. Backmarking improves the efficiency of checking consistency. Backjumping allows saving part of the search by backtracking "more than one variable" in some cases.
In mathematical optimization and computer science, heuristic (from Greek εὑρίσκω "I find, discover" [1]) is a technique designed for problem solving more quickly when classic methods are too slow for finding an exact or approximate solution, or when classic methods fail to find any exact solution in a search space.
If h a (n) is an admissible heuristic function, in the weighted version of the A* search one uses h w (n) = ε h a (n), ε > 1 as the heuristic function, and perform the A* search as usual (which eventually happens faster than using h a since fewer nodes are expanded).
Variable neighborhood search (VNS), [1] proposed by Mladenović & Hansen in 1997, [2] is a metaheuristic method for solving a set of combinatorial optimization and global optimization problems. It explores distant neighborhoods of the current incumbent solution, and moves from there to a new one if and only if an improvement was made.
Matheuristics [1] [2] are problem agnostic optimization algorithms that make use of mathematical programming (MP) techniques in order to obtain heuristic solutions. Problem-dependent elements are included only within the lower-level mathematic programming, local search or constructive components.
It is a direct search method (based on function comparison) and is often applied to nonlinear optimization problems for which derivatives may not be known. However, the Nelder–Mead technique is a heuristic search method that can converge to non-stationary points [1] on problems that can be solved by alternative methods. [2]