Statistical mechanics analysis of general multi-dimensional knapsack problems

TL;DR

This paper uses statistical mechanics to analyze the generalized multidimensional knapsack problem, revealing how profit limits scale and proposing heuristics that approach optimal solutions efficiently.

Contribution

It provides a novel statistical mechanics framework for GMDKP, analyzing solution properties and developing heuristics based on the cavity method.

Findings

Profit scales with the number of item types and choices per type.

A greedy heuristic nearly achieves optimal profit with low computational cost.

Heuristic algorithms based on the cavity method improve solution quality.

Abstract

Knapsack problem (KP) is a representative combinatorial optimization problem that aims to maximize the total profit by selecting a subset of items under given constraints on the total weights. In this study, we analyze a generalized version of KP, which is termed the generalized multidimensional knapsack problem (GMDKP). As opposed to the basic KP, GMDKP allows multiple choices per item type under multiple weight constraints. Although several efficient algorithms are known and the properties of their solutions have been examined to a significant extent for basic KPs, there is a paucity of known algorithms and studies on the solution properties of GMDKP. To gain insight into the problem, we assess the typical achievable limit of the total profit for a random ensemble of GMDKP using the replica method. Our findings are summarized as follows: (1) When the profits of item types are normally distributed, the total profit grows in the leading order with respect to the number of item types as the maximum number of choices per item type $x^{\rm max}$ increases while it depends on $x^{\rm max}$ only in a sub-leading order if the profits are constant among the item types. (2) A greedy-type heuristic can find a nearly optimal solution whose total profit is lower than the optimal value only by a sub-leading order with a low computational cost. (3) The sub-leading difference from the optimal total profit can be improved by a heuristic algorithm based on the cavity method. Extensive numerical experiments support these findings.