摘要：A popular strategy used by many exact or heuristic search algorithms (e.g., Branch & Bound, A* search algorithm, etc) is to follow down one path in the tree until either a feasible solution is found or else fathoming occurs. For a minimization problem, the lower bounds calculated at various tree nodes tend to be well below the optimal value of the objective function, let alone the values of the successively improving upper bounds. As a result fathoming usually occurs only deep in the tree, and consequently, the search becomes rather lengthy. The purpose of introducing variable upper bound techniques is to make use of variable "fictitious" upper bounds in a systematic way so that optimal and suboptimal solutions can be obtained with a relatively smaller computational effort.
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