On-Line Bin-Stretching

We are given a sequence of items that can be packed into m unit size bins. In the classical bin packing problem we x the size of the bins and try to pack the items in the minimum number of such bins. In contrast, in the bin-stretching problem we x the number of bins and try to pack the items while stretching the size of the bins as least as possible. We present two on-line algorithms for the bin-stretching problem that guarantee a stretching factor of 5=3 for any number m of bins. We then combine the two algorithms and design an algorithm whose stretching factor is 1:625 for any m. The analysis for the performance of this algorithm is tight. The best lower bound for any algorithm is 4=3 for any m 2. We note that the bin-stretching problem is also equivalent to the classical scheduling (load balancing) problem in which the value of the makespan (maximum load) is known in advance.