Treffer: Improved Algorithms for Variants of Bin Packing and Knapsack.
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We study variants of two classical optimization problems: Bin Packing and Knapsack. Both bin packing and knapsack fall under the regime of "Packing and Covering Problems". In bin packing, we are given a set of input items, each with an associated size, and the objective is to pack these into the minimum number of unit capacity bins. On the other hand, in the knapsack problem, each item has an additional profit associated with it. The objective is to find a maximum profitable subset that can be packed into a unit capacity knapsack. Both bin packing and knapsack find numerous applications; however, both turn out to be NP-Hard. Hence, it is natural to seek approximation algorithms for these problems. Lawler settled the knapsack problem by giving an FPTAS, whereas the progressive works of de la Vega and Lueker, Karmarkar and Karp, and Rothvoss have given improved approximation schemes for the bin packing problem. However, many variants of these problems (e.g., multidimensional, geometric, stochastic) also find wide applicability, but haven't been settled. We make progress on this front by providing new and improved algorithms for several such variants. First, we study bin packing under the i.i.d. model, where item sizes are sampled independently and identically from a distribution in (0,1]. Both the distribution and the total number of items are unknown. The items arrive one by one, and their sizes are revealed upon their arrival, and they must be packed immediately and irrevocably in bins of unit size. We provide a simple meta-algorithm that takes an offline \alpha-asymptotic approximation algorithm and provides a polynomial-time (\alpha+\epsilon)-competitive algorithm for online bin packing under the i.i.d. model, where \epsilon>0 is a small constant. Using the AFPTAS for offline bin packing, we thus provide a linear time (1+\epsilon)-competitive algorithm for online bin packing under the i.i.d. model, thus settling the problem. Then we study a well-known geometric generalization of the knapsack problem, the ...