A subset selection problem from a finite set of items is considered, where a constraint is imposed on the cardinality of a selected subset. The subset selection problem is motivated by automated packaging systems, so-...
详细信息
ISBN:
(纸本)9781538626337
A subset selection problem from a finite set of items is considered, where a constraint is imposed on the cardinality of a selected subset. The subset selection problem is motivated by automated packaging systems, so-called multi-head weighers. Given a set of n items with their integral weights, a positive integer target weight t and a positive integer k, the subset selection problem asks to find a subset of the items so that the total weight of chosen items is no less than the target weight, and the number of the chosen items is exactly k, and further the total weight of them is as close to the target weight as possible. In this paper, an O(knt) time algorithm is presented to solve the subset selection problem. Numerical experiments are also conducted to demonstrate the performance of the pseudo-polynomialtime algorithm on certain test instances having a feasible solution, and the results are reported.
We investigate pseudo-polynomial time algorithms for Subset Sum. Given a multi-set X of n positive integers and a target t, Subset Sum asks whether some subset of X sums to t. Bringmann proposes an (O) over tilde (n +...
详细信息
ISBN:
(纸本)9798331516758;9798331516741
We investigate pseudo-polynomial time algorithms for Subset Sum. Given a multi-set X of n positive integers and a target t, Subset Sum asks whether some subset of X sums to t. Bringmann proposes an (O) over tilde (n + t)-time algorithm [Bringmann SODA'17], and an open question has naturally arisen: can Subset Sum be solved in O(n+w) time? Here w is the maximum integer in X. We make a progress towards resolving the open question by proposing an (O) over tilde (n + root wt)-time algorithm.
Given a tree T = (V, E) of n nodes such that each node v is associated with a value-weight pair (val(v), w(v)), where value val(v) is a real number and weight w(v) is a non-negative integer, the density of T is define...
详细信息
Given a tree T = (V, E) of n nodes such that each node v is associated with a value-weight pair (val(v), w(v)), where value val(v) is a real number and weight w(v) is a non-negative integer, the density of T is defined as Sigma(v is an element of V) val(v)/Sigma(v is an element of V) w(v). A subtree of T is a connected subgraph (V', E') of T, where V' subset of V and E' subset of E. Given two integers w(min) and w(max), the weight-constrained maximum-density subtree problem on T is to find a maximum-density subtree T' = (V', E') satisfying w(min) <= Sigma(v is an element of V')w(v) <= W-max. In this paper, we first present an O(w(max)n)-time algorithm to find a weight-constrained maximum-density path in a tree T, and then present an O (w(max)(2)n)-time algorithm to find a weight-constrained maximum-density subtree in T. Finally, given a node subset S subset of V, we also present an O(w(max)(2)n)-time algorithm to find a weight-constrained maximum-density subtree in T which covers all the nodes in S.
Simple Temporal Networks (STNs) provide a powerful and general tool for representing conjunctions of maximum delay constraints over ordered pairs of temporal variables. In this paper we introduce Hyper Temporal Networ...
详细信息
Simple Temporal Networks (STNs) provide a powerful and general tool for representing conjunctions of maximum delay constraints over ordered pairs of temporal variables. In this paper we introduce Hyper Temporal Networks (HyTNs), a strict generalization of STNs, to overcome the limitation of considering only conjunctions of constraints but maintaining a practical efficiency in the consistency check of the instances. In a Hyper Temporal Network a single temporal hyperarc constraint may be defined as a set of two or more maximum delay constraints which is satisfied when at least one of these delay constraints is satisfied. HyTNs are meant as a light generalization of STNs offering an interesting compromise. On one side, there exist practical pseudo-polynomial time algorithms for checking consistency and computing feasible schedules for HyTNs. On the other side, HyTNs offer a more powerful model accommodating natural constraints that cannot be expressed by STNs like "Trigger off exactly delta min before (after) the occurrence of the first (last) event in a set.", which are used to represent synchronization events in some process aware information systems/workflow models proposed in the literature.
We study a problem related to finding shortest paths in weighted graphs. We, ask whether or not there is a path between two nodes that has a given total cost k. The edge weights of the graph can be both positive and n...
详细信息
We study a problem related to finding shortest paths in weighted graphs. We, ask whether or not there is a path between two nodes that has a given total cost k. The edge weights of the graph can be both positive and negative integers or even integer vectors. We show that many variants of this problem are NP-complete. We develop a pseudo-polynomial algorithm for (both positive and negative) integer weights. The running time of this algorithm is O(W(2)n(3) + \k\ min(\k\, W)n(2)), where n is the number of nodes in the graph, W is the largest absolute value of any edge weight, and k is the target cost. The algorithm is based on preprocessing the graph with a relaxation algorithm to eliminate the effects of weight sign alternations along a path. This preprocessing stage is applicable to other problems as well. For example, we show how to find the minimum absolute cost of any path between two given nodes in a graph with integer weights in O(W(2)n(3)) time. (C) 2002 Elsevier Science.
The lexicographic bi-criteria combinatorial optimization problem to be discussed in this paper is a mathematical model of the food mixture packing performed by so-called automatic combination weighers, and it is descr...
详细信息
The lexicographic bi-criteria combinatorial optimization problem to be discussed in this paper is a mathematical model of the food mixture packing performed by so-called automatic combination weighers, and it is described as follows. We are given a union I = I-1 boolean OR I-2 boolean OR . . . boolean OR I-m of m sets of items, where for each i = 1, 2,...,m, I-i = {I-ik vertical bar k = 1,2,...,n denotes a set of n items of the i-th type and I-ik denotes the k-th item of the i-th type. Each item I-ik has an integral weight w(ik) and an integral priority gamma(ik). The problem asks to find a union = I' = I'(1) boolean OR I'(2) boolean OR . . . boolean OR I'(m) of m subsets of items where I'(i) subset of I-i so that the total weight of chosen items for I' is no less than an integral target weight T, and the sum weight of chosen items of the i-th type for is no less than an integral indispensable weight b(i). The total weight of chosen items for I' is minimized as the primary objective, and further the total priority of chosen items for I' is maximized as the second objective. For the case in which there are two types of items (i.e., m = 2), we propose an O(nT) time dynamic programming algorithm, applying a linear search technique. We also conduct numerical experiments to demonstrate the empirical performance.
The packing system performs an operation of choosing a subset I ' from the set of I of the current n items to produce a package of foods. By repeating the packing operation, it produces a large number of packages ...
详细信息
The packing system performs an operation of choosing a subset I ' from the set of I of the current n items to produce a package of foods. By repeating the packing operation, it produces a large number of packages one by one. The primary objective is to choose a subset I so that the total weight of chosen items is as close to a specified target weight T as possible. We additionally try to maximise the total priority of chosen items as the second objective so that items with longer durations in hoppers are preferably chosen. We show that the combinatorial food packing problem can be solved in O(nT) time if all input data are integral.
The subject of the paper is to give an overview and latest results on the Legal Firing Sequence Problem of Petri nets (LFS for short). LFS is very fundamental in the sense that it appears as a subproblem or a simpler ...
详细信息
The subject of the paper is to give an overview and latest results on the Legal Firing Sequence Problem of Petri nets (LFS for short). LFS is very fundamental in the sense that it appears as a subproblem or a simpler form of various basic: problems in Petri net. theory, such as the weil-known marking reachability problem, the minimum initial resource allocation problem, the liveness (of level 4) problem, the scheduling problem md so on. However, solving LFS generally is not easy: it is SP-hard even for Petri nets having very simple structures. This intractability of LFS may have been preventing us from producing efficient algorithms for those problems. So research on LFS from computational complexity point of view seems to be rewarding.
暂无评论