Abstract
This paper explores reoptimization techniques for solving sequences of similar mixed integer programs (MIPs) more effectively. Traditionally, these MIPs are solved independently, without capitalizing on information from previously solved instances. Our approach focuses on primal bound improvements by reusing the solutions of the previously solved instances, as well as dual bound improvements by reusing the branching history and automating parameter tuning. We also describe ways to improve the solver performance by extending ideas from reliability branching to generate better pseudocosts. Our reoptimization approach, crafted for the MIP 2023 workshop computational competition, was honored with the first prize. In this paper, we thoroughly analyze the performance of each technique and their combined impact on the solver’s performance. Finally, we present ways to extend our techniques in practice for further improvements.
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Data availability
The datasets analysed for the current study are available in the github repository, https://github.com/krooonal/mipcc2023/tree/MPCPaper.
Code availability
The code used for the current study is available in the github repository, https://github.com/krooonal/mipcc2023/tree/MPCPaper.
Notes
For the series RHS 2 and RHS 4, the shifted geometric means of solving times are higher than the time limit. This indicates that SCIP could not solve most of these instances in the given time limit.
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Acknowledgements
The author received financial support from the Canada Excellence Research Chair (CERC), Polytechnique Montreal and the computational resources for experimental evaluation were provided by CERC. The author would also like to thank Prof. Andrea Lodi, Prof. Guy Desaulniers, and the anonymous reviewers for their helpful comments.
Funding
Partial financial support was received from Canada Excellence Research Chair (CERC), Polytechnique Montreal. The computational resources for experimental evaluation were provided by CERC.
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Krunal Kishor Patel designed, implemented, and tested the ideas presented in this paper.
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Appendix: Detailed results
Appendix: Detailed results
We present the aggregated statistics for techniques presented in this paper in Table 17 (grouped by changing component), Table 18 (grouped by geometric mean of solve time in BASE), and Table 19 (grouped by BASE score). Each table shows the aggregated BASE total score and percentage improvements caused by each technique. Since the number of series for each group is too small, we advise readers to be cautious while making generalized conclusions based on these tables (e.g., TURNOFF works best when RHS is changing).
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Patel, K.K. Progressively strengthening and tuning MIP solvers for reoptimization. Math. Prog. Comp. (2024). https://doi.org/10.1007/s12532-024-00253-z
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DOI: https://doi.org/10.1007/s12532-024-00253-z