Triangular Grid Instances for the Euclidean Steiner Tree Problem

This data set contains triangular nxk arrays with 2<=n, k<=10 using the TSPLIB-format. The instances where generated as part of the master's thesis of Daphne Rohrssen written 2022 under the supervision of Stefan Hougardy at the University of Bonn. Some of these instances are very hard to solve exactly for GeoSteiner 5.1. For example the 4x9 instance with 36 vertices needs more than 10 days of CPU time. SCIP-JACK 2.1 solves this instance within 20 minutes. However, one should be aware of the fact that both codes have numerical problems and cannot guarantee optimality of the solutions. With SCIP-JACK this seems to happen more often than with GeoSteiner.