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Possible algorithmic improvements #5

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In Clautiaux, F., Carlier, J., & Moukrim, A. (2007). A new exact method for the two-dimensional orthogonal packing problem. European Journal of Operational Research, 183(3), 1196-1211, it was observed that hard instances exhibit a low area waste (epsilon) in the range of 2%-7%, i.e., the sum of item areas is close the area of the bin.

From our observation, the hardest instances appear to be those that only contain items that are smaller than half of the the bin's width and height, whereas epsilon might play an additional complicating factor. This can be explained by the fact that many preprocessing and simplification techniques leverage items that are larger than half the bin dimension. Consequently, the absence of those items increases the complexity. For a collection of such instances see https://github.com/ktnr/TwoStepBranchingProcedure/tree/main/data/input/BPP-Subproblems. They are derived from subproblems of hard 2D bin packing instances that are solved by branch-and-cut. If those 2D-OPP instances can be solved efficiently, it opens the door to also close some of the hard 2D bin packing instances that still remain open after more than 30 years since they have been first introduced.

Relevant references for ideas to improve solution times for problematic 2D-OPP instances with numerous small items using ideas from:

Feel free to get in touch if you want to talk about improvements or contribute.

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