Gioni Mexi

My research interests include primal heuristics, generalization of conflict analysis techniques in mixed-integer programming, and the integration of different solver technologies.

📬 Contact

office
Room 3101 at ZIB
e-mail

🎓 Curriculum vitae

since 2021
Researcher at ZIB
Jul 2021
M.Sc. at TUB
Mar 2019
B.Sc. in Mathematics at TUB

đź“ť Publications and preprints

Preprints

  1. Bolusani, S., Besançon, M., Bestuzheva, K., Chmiela, A., Dionísio, J., Donkiewicz, T., van Doornmalen, J., Eifler, L., Ghannam, M., Gleixner, A., Graczyk, C., Halbig, K., Hedtke, I., Hoen, A., Hojny, C., van der Hulst, R., Kamp, D., Koch, T., Kofler, K., … Xu, L. (2024). The SCIP Optimization Suite 9.0 (ZIB Report No. 24-02-29). Zuse Institute Berlin. [URL] [arXiv] [code]
    [BibTeX]
    @techreport{2024_BolusaniEtAl_Scip9,
      year = {2024},
      institution = {Zuse Institute Berlin},
      type = {ZIB Report},
      month = feb,
      number = {24-02-29},
      url = {https://nbn-resolving.org/urn:nbn:de:0297-zib-95528},
      archiveprefix = {arXiv},
      eprint = {2402.17702},
      primaryclass = {math.OC},
      author = {Bolusani, Suresh and Besançon, Mathieu and Bestuzheva, Ksenia and Chmiela, Antonia and Dionísio, João and Donkiewicz, Tim and van Doornmalen, Jasper and Eifler, Leon and Ghannam, Mohammed and Gleixner, Ambros and Graczyk, Christoph and Halbig, Katrin and Hedtke, Ivo and Hoen, Alexander and Hojny, Christopher and van der Hulst, Rolf and Kamp, Dominik and Koch, Thorsten and Kofler, Kevin and Lentz, Jurgen and Manns, Julian and Mexi, Gioni and Mühmer, Erik and Pfetsch, Marc and Schlösser, Franziska and Serrano, Felipe and Shinano, Yuji and Turner, Mark and Vigerske, Stefan and Weninger, Dieter and Xu, Liding},
      title = {The SCIP Optimization Suite 9.0},
      code = {https://scipopt.org}
    }
  2. Bolusani, S., Mexi, G., Besançon, M., and Turner, M. (2024). A Multi-Reference Relaxation Enforced Neighborhood Search Heuristic in SCIP. [arXiv]
    [BibTeX]
    @misc{2024_BolusaniMexiBesanconTurner_Multireferenceneighborhoodsearch,
      archiveprefix = {arXiv},
      eprint = {2408.00718},
      primaryclass = {math.OC},
      year = {2024},
      author = {Bolusani, Suresh and Mexi, Gioni and Besançon, Mathieu and Turner, Mark},
      title = {A Multi-Reference Relaxation Enforced Neighborhood Search Heuristic in SCIP}
    }
  3. Mexi, G., Serrano, F., Berthold, T., Gleixner, A., and Nordström, J. (2024). Cut-based Conflict Analysis in Mixed Integer Programming. [arXiv]
    [BibTeX]
    @misc{2024_MexiSerranoBertholdGleixnerNordstroem_Cutbasedconflictanalysis,
      archiveprefix = {arXiv},
      eprint = {2410.15110},
      primaryclass = {math.OC},
      year = {2024},
      author = {Mexi, Gioni and Serrano, Felipe and Berthold, Timo and Gleixner, Ambros and Nordström, Jakob},
      title = {Cut-based Conflict Analysis in Mixed Integer Programming}
    }

Conference proceedings

  1. Mexi, G., Shamsi, S., Besançon, M., and le Bodic, P. (2024). Probabilistic Lookahead Strong Branching Via a Stochastic Abstract Branching Model. Proceedings of the International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research. [arXiv]
    [BibTeX]
    @inproceedings{2023_MexiSomayehBesanconPierre_Probabilisticstrongbranching,
      year = {2024},
      booktitle = {Proceedings of the International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research},
      archiveprefix = {arXiv},
      eprint = {2312.07041},
      primaryclass = {math.OC},
      author = {Mexi, Gioni and Shamsi, Somayeh and Besançon, Mathieu and le Bodic, Pierre},
      title = {Probabilistic Lookahead Strong Branching Via a Stochastic Abstract Branching Model}
    }
  2. Ghannam, M., Mexi, G., Lam, E., and Gleixner, A. (2024). Branch and Price for the Length-constrained Cycle Partition Problem. Proceedings of the INFORMS Optimization Society Conference. [URL] [arXiv]
    [BibTeX]
    @inproceedings{2024_GhannamMexiLamGleixner_Branchpricelccp,
      year = {2024},
      booktitle = {Proceedings of the INFORMS Optimization Society Conference},
      url = {https://sites.google.com/view/ios2024refereed},
      archiveprefix = {arXiv},
      eprint = {2401.17937},
      primaryclass = {math.OC},
      author = {Ghannam, Mohammed and Mexi, Gioni and Lam, Edward and Gleixner, Ambros},
      title = {Branch and Price for the Length-constrained Cycle Partition Problem}
    }
  3. Mexi, G., Berthold, T., Gleixner, A., and Nordström, J. (2023). Improving Conflict Analysis in MIP Solvers by Pseudo-Boolean Reasoning. Proceedings of the 29th International Conference on Principles and Practice of Constraint Programming (CP 2023), 280, 27:1–27:19, DOI: 10.4230/LIPIcs.CP.2023.27 [arXiv]
    [BibTeX]
    @inproceedings{2023_MexiBertholdGleixnerNordstrm_ConflictanalysisPseudoboolean,
      year = {2023},
      booktitle = {Proceedings of the 29th International Conference on Principles and Practice of Constraint Programming (CP 2023)},
      volume = {280},
      pages = {27:1-27:19,},
      doi = {10.4230/LIPIcs.CP.2023.27},
      archiveprefix = {arXiv},
      eprint = {2307.14166},
      primaryclass = {math.OC},
      author = {Mexi, Gioni and Berthold, Timo and Gleixner, Ambros and Nordström, Jakob},
      title = {Improving Conflict Analysis in MIP Solvers by Pseudo-Boolean Reasoning}
    }
  4. Mexi, G., Besançon, M., Bolusani, S., Chmiela, A., Hoen, A., and Gleixner, A. (2023). Scylla: a Matrix-free Fix-propagate-and-project Heuristic for Mixed-integer Optimization. Proceedings of the Conference of the Society for Operations Research in Germany. [arXiv]
    [BibTeX]
    @inproceedings{2023_MexiEtAl_Scyllaheuristic,
      year = {2023},
      booktitle = {Proceedings of the Conference of the Society for Operations Research in Germany},
      archiveprefix = {arXiv},
      eprint = {2307.03466},
      primaryclass = {math.OC},
      author = {Mexi, Gioni and Besançon, Mathieu and Bolusani, Suresh and Chmiela, Antonia and Hoen, Alexander and Gleixner, Ambros},
      title = {Scylla: a Matrix-free Fix-propagate-and-project Heuristic for Mixed-integer Optimization}
    }
  5. Hoppmann-Baum, K., Mexi, G., Burdakov, O., Casselgren, C. J., and Koch, T. (2020). Minimum Cycle Partition with Length Requirements. Proceedings of the International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research, 12296, 273–282. DOI: 10.1007/978-3-030-58942-4_18
    [BibTeX]
    @inproceedings{2020_HoppmannEtAl_Minimumcyclepartition,
      year = {2020},
      booktitle = {Proceedings of the International Conference on the Integration of Constraint Programming, Artificial Intelligence, and Operations Research},
      volume = {12296},
      pages = {273-282},
      doi = {10.1007/978-3-030-58942-4_18},
      author = {Hoppmann-Baum, Kai and Mexi, Gioni and Burdakov, Oleg and Casselgren, Carl Johan and Koch, Thorsten},
      title = {Minimum Cycle Partition with Length Requirements}
    }

Full articles

  1. Berthold, T., Mexi, G., and Salvagnin, D. (2023). Using Multiple Reference Vectors and Objective Scaling in the Feasibility Pump. EURO Journal on Computational Optimization, 11. DOI: 10.1016/j.ejco.2023.100066
    [BibTeX]
    @article{2023_BertholdMexiSalvagnin_Multiplereferencevectors,
      year = {2023},
      journal = {EURO Journal on Computational Optimization},
      volume = {11},
      doi = {10.1016/j.ejco.2023.100066},
      author = {Berthold, Timo and Mexi, Gioni and Salvagnin, Domenico},
      title = {Using Multiple Reference Vectors and Objective Scaling in the Feasibility Pump}
    }
  2. Hoppmann-Baum, K., Burdakov, O., Mexi, G., Casselgren, C. J., and Koch, T. (2022). Length-Constrained Cycle Partition with an Application to UAV Routing. Optimization Methods and Software. DOI: 10.1080/10556788.2022.2053972
    [BibTeX]
    @article{2022_HoppmannEtAl_CyclepartitionUavrouting,
      year = {2022},
      journal = {Optimization Methods and Software},
      doi = {10.1080/10556788.2022.2053972},
      author = {Hoppmann-Baum, Kai and Burdakov, Oleg and Mexi, Gioni and Casselgren, Carl Johan and Koch, Thorsten},
      title = {Length-Constrained Cycle Partition with an Application to UAV Routing}
    }

🔬 Projects

Research Campus MODAL SynLab

SynLab researches mathematical generalization of application-specific advances achieved in the Gas-, Rail– and MedLab of the research campus MODAL. The focus is on exact methods for solving a broad class of discrete-continuous optimization problems. This requires advanced techniques for structure recognition, consideration of nonlinear restrictions from practice, and the efficient implementation of mathematical algorithms on modern computer architectures. The results are bundled in a professional software package and complemented by a range of high-performance methods for specific applications with a high degree of innovation.

SynLab
Apr 2020 to Mar 2025
13
53

đź’¬ Talks and posters

Conference and workshop talks

Jul 2024
Generalized Resolution Conflict Analysis in MIP Solvers
25th International Symposium on Mathematical Programming (ISMP), Montréal
May 2024
Probabilistic Lookahead Strong Branching Via a Stochastic Abstract Branching Model
21st CPAIOR Conference, Uppsala
Apr 2024
Updates in SCIP 9
SAP-ZIB-FAU Workshop, Walldorf
Aug 2023
Improving Conflict Analysis in MIP Solvers by Pseudo-Boolean Reasoning
29th CP Conference, Toronto [PDF]
Jul 2023
Improving Conflict Analysis in MIP Solvers by Pseudo-Boolean Reasoning
14th Pragmatics of SAT international workshop [PDF]
Jan 2023
Recent Advances in SCIP
SAP-ZIB-FAU Workshop, Walldorf
Jul 2022
Feasibility Pump Using Multiple Reference Vectors And New Scaling
32nd European Conference on Operational Research (EURO), Espoo

Research seminar talks

Feb 2025
TBD
IOL Research Seminar (IOL), Berlin

đź“… Event Attendance