Tuesday, 02.09.2025, 14.30-16.00
Hexaly Workshop: Modeling and Solving Packing Problems with Hexaly Studio
Léa Blaise, Bienvenu Bambi, Michael Feldmeier, Leona Gottwald
Hexaly Optimizer is a global mathematical solver that integrates both exact and heuristic techniques to tackle complex optimization problems. At its core is an innovative modeling formalism based on nonlinear and set-oriented expressions, enabling users to write compact, expressive models for a wide variety of optimization problems. This formalism not only simplifies the modeling process but also provides the solver with higher-level structural information, allowing it to leverage advanced algorithmic techniques from the literature to obtain state-of-the-art performance on classic optimization domains such as routing, scheduling, and packing.
In this hands-on workshop, we will focus on the application of Hexaly to packing problems, showcasing how the solver’s set-based modeling capabilities naturally align with the structure of these problems. Participants will be guided through building and solving real-world packing problems using Hexaly Studio, a web-based integrated development environment designed specifically for optimization modeling. Hexaly Studio features intuitive dashboards, interactive widgets, and graphical solution visualizations, making it easy to both formulate models and interpret results. Through guided examples and interactive problem-solving, participants will gain hands-on experience with Hexaly and will be equipped to explore it further in their own research or applied projects.
If you are planning to attend the workshop, please write to contact@hexaly.com.
Keywords: Software for OR/MS Analysis, Cutting and Packing
Tuesday, 02.09.2025, 16.30-18.00
GAMSPy Workshop: An Introduction to Modelling with GAMSPy
Frederik Fiand, Lutz Westermann
This 90-minute workshop offers a hands-on introduction to GAMSPy. GAMSPy combines the high-performance GAMS execution system with the flexible Python language, creating a powerful mathematical optimization package. It acts as a bridge between the expressive Python language and the robust GAMS system, allowing you to create complex mathematical models effortlessly.
Join us to explore GAMSPy’s fundamental functionalities through practical, interactive exercises. We’ll cover everything from defining sets, parameters, variables, and equations to solving models and retrieving results, all within a familiar Python environment. Beyond the basics, we’ll also provide a glimpse into more advanced features, demonstrating how GAMSPy can streamline complex modeling workflows and enhance your analytical capabilities.
Whether you’re a seasoned GAMS user looking to integrate with Python or a Python user curious about optimization, this workshop will equip you with the essential skills to get started with GAMSPy.
If you would like to participate in the workshop, please send an e-mail with the subject “GAMSPy Workshop – OR 2025” to or2025@gams.com.
Keywords: Mathematical Programming, Modeling Systems and Languages, Software for OR/MS Analysis
Wednesday, 03.09.2025, 15.15-16.00
Gurobi Workshop: Solving LPs and MIPs with Gurobi on the GPU: What’s in for me?
Robert Luce
Recent GPU hardware generations offer high compute throughput for many applications in machine learning, scientific computing, and beyond. How does this new compute power translate into improvements in solving real-world linear and mixed-integer optimization problems in practice?
In this workshop, we review Gurobi’s efforts and research findings on solving optimization problems on the GPU. We touch interior point methods, first-order methods, and relaxation-based MIP heuristics, and we frame these in terms of their applicability and usability on the GPU. Also, we discuss a few implementation aspects that only arise when implementing such traditional methods on the GPU.
Finally, we’ll showcase how Gurobi’s preliminary GPU-based components compare, performance-wise, to our standard CPU-based counterparts across a wide range of real-world models.
Keywords: Computational Experiments, Large Scale Optimization, Linear Programming
Friday, 05.09.2025, 10.45-11.30
Hexaly Lecture: Hexaly, a new kind of global optimization solver
Léa Blaise
Hexaly Optimizer is a new kind of global optimization solver. Its modeling interface is nonlinear and set-oriented. In a sense, Hexaly APIs unify and extend modeling concepts from mixed-linear programming, nonlinear programming, and constraint programming. Under the hood, Hexaly combines various exact and heuristic optimization methods, such as branch-and-bound, automatic Dantzig-Wolfe reformulation, column and row generation, propagation methods, local search, direct search, and surrogate modeling techniques.
Regarding performance benchmarks, Hexaly distinguishes itself against the leading solvers in the market, like Gurobi, IBM Cplex, and Google OR Tools, by delivering fast and scalable solutions to Routing, Scheduling, Packing, Clustering, and Location problems.
This talk will introduce our set-based modeling formalism and show its scalability for large instances. We will then explore how the solver can use this formalism to automatically use state-of-the-art resolution techniques from the exact and heuristic fields.
Keyword: Software for OR/MS Analysis