67 citations · 72 across the 23 of their papers we have counts for
24 papers
A computational comparison of handling distance constraints in MINLP
Christopher Hojny, Leo Liberti
Minimum distance constraints (minDCs) appear in many geometric optimization problems. They pose major challenges for mixed-integer nonlinear programming (MINLP) due to their revers…
The SCIP Optimization Suite 10.0
Christopher Hojny, Mathieu Besançon, Ksenia Bestuzheva +31
The SCIP Optimization Suite provides a collection of software packages for mathematical optimization, centered around the constraint integer programming (CIP) framework SCIP. This…
On the Expressiveness of Rational ReLU Neural Networks With Bounded Depth
Gennadiy Averkov, Christopher Hojny, Maximilian Merkert
To confirm that the expressive power of ReLU neural networks grows with their depth, the function has been considered in the literature. A conject…
State-of-the-art Methods for Pseudo-Boolean Solving with SCIP
Gioni Mexi, Dominik Kamp, Yuji Shinano +8
The Pseudo-Boolean problem deals with linear or polynomial constraints with integer coefficients over Boolean variables. The objective lies in optimizing a linear objective functio…
Detecting and Handling Reflection Symmetries in Mixed-Integer (Nonlinear) Programming
Christopher Hojny
Symmetries in mixed-integer (nonlinear) programs (MINLP), if not handled appropriately, are known to negatively impact the performance of (spatial) branch-and-bound algorithms. Usu…
The SCIP Optimization Suite 9.0
Suresh Bolusani, Mathieu Besançon, Ksenia Bestuzheva +28
The SCIP Optimization Suite provides a collection of software packages for mathematical optimization, centered around the constraint integer programming (CIP) framework SCIP. This…
Fairness in Graph-Theoretical Optimization Problems
Christopher Hojny, Frits Spieksma, Sten Wessel
There is arbitrariness in optimum solutions of graph-theoretic problems that can give rise to unfairness. Incorporating fairness in such problems, however, can be done in multiple…
A proof system for certifying symmetry and optimality reasoning in integer programming
Jasper van Doornmalen, Leon Eifler, Ambros Gleixner +1
We present a proof system for establishing the correctness of results produced by optimization algorithms, with a focus on mixed-integer programming (MIP). Our system generalizes t…
The Impact of Symmetry Handling for the Stable Set Problem via Schreier-Sims Cuts
Christopher Hojny, Annika Jäger, Marc E. Pfetsch +1
Symmetry handling inequalities (SHIs) are an appealing and popular tool for handling symmetries in integer programming. Despite their practical application, little is known about t…
Enabling Research through the SCIP Optimization Suite 8.0
Ksenia Bestuzheva, Mathieu Besançon, Wei-Kun Chen +32
The SCIP Optimization Suite provides a collection of software packages for mathematical optimization centered around the constraint integer programming framework SCIP. The focus of…
Network Coding: An Optimization Approach
Christopher Hojny, Altan B. Kilic, Alberto Ravagnani
We consider the problem of computing the capacity of a coded, multicast network over a small alphabet. We introduce a novel approach to this problem based on mixed integer programm…
Handling Sub-symmetry in Integer Programming using Activation Handlers
Christopher Hojny, Tom Verhoeff, Sten Wessel
Symmetry in integer programs (IPs) can be exploited in order to reduce solving times. Usually only symmetries of the original IP are handled, but new symmetries may arise at some n…
A Unified Framework for Symmetry Handling
Jasper van Doornmalen, Christopher Hojny
Handling symmetries in optimization problems is essential for devising efficient solution methods. In this article, we present a general framework that captures many of the already…
Integer Programming Models for Round Robin Tournaments
Jasper van Doornmalen, Christopher Hojny, Roel Lambers +1
Round robin tournaments are omnipresent in sport competitions and beyond. We propose two new integer programming formulations for scheduling a round robin tournament, one of which…
A flow-based formulation for parallel machine scheduling using decision diagrams
Daniel Kowalczyk, Roel Leus, Christopher Hojny +1
We present a new flow-based formulation for identical parallel machine scheduling with a regular objective function and without idle time. The formulation is constructed with the h…
The role of rationality in integer-programming relaxations
Manuel Aprile, Gennadiy Averkov, Marco Di Summa +1
For a finite set that can be represented as for some polyhedron , we call a relaxation of and define the relaxation co…
Efficient MIP Techniques for Computing the Relaxation Complexity
Gennadiy Averkov, Christopher Hojny, Matthias Schymura
The relaxation complexity rc(X) of the set of integer points X contained in a polyhedron is the minimal number of inequalities needed to formulate a linear optimization problem ove…
Efficient Propagation Techniques for Handling Cyclic Symmetries in Binary Programs
Jasper van Doornmalen, Christopher Hojny
The presence of symmetries of binary programs typically degrade the performance of branch-and-bound solvers. In this article, we derive efficient variable fixing algorithms to disc…
Schreier-Sims Cuts meet Stable Set: Preserving Problem Structure when Handling Symmetries
Christopher Hojny, Marc E. Pfetsch, José Verschae
Symmetry handling inequalities (SHIs) are a popular tool to handle symmetries in integer programming. Despite their successful application in practice, only little is known about t…
Characterizing and computing weight-equitable partitions of graphs
Aida Abiad, Christopher Hojny, Sjanne Zeijlemaker
Weight-equitable partitions of graphs, which are a natural extension of the well-known equitable partitions, have been shown to be a powerful tool to weaken the regularity assumpti…
Computational Aspects of Relaxation Complexity: Possibilities and Limitations
Gennadiy Averkov, Christopher Hojny, Matthias Schymura
The relaxation complexity of the set of integer points contained in a polyhedron is the smallest number of facets of any polyhedron such that the integer p…
Cutting Plane Approaches for the Robust Kidney Exchange Problem
Danny Blom, Christopher Hojny, Bart Smeulders
Renal patients which have a willing but incompatible donor can decide to participate in a kidney exchange program (KEP). The goal of a KEP is to identify sets of such incompatible…
A Simple Method for Convex Optimization in the Oracle Model
Daniel Dadush, Christopher Hojny, Sophie Huiberts +1
We give a simple and natural method for computing approximately optimal solutions for minimizing a convex function over a convex set given by a separation oracle. Our metho…
Integrality of Linearizations of Polynomials over Binary Variables using Additional Monomials
Christopher Hojny, Marc E. Pfetsch, Matthias Walter
Polynomial optimization problems over binary variables can be expressed as integer programs using a linearization with extra monomials in addition to those arising in the given pol…