PACE2019: Track 1 - Vertex Cover Instances

Instances for the PACE Challenge 2019 on the Track 1a: Vertex Cover. The odd instances (001.hgr, 003.hgr, ...) were made public for all participants during the testing phase of the solvers, whereas the private instances (002.hgr, 004.hgr, ...) were used for the final evaluation and disclosed after the submission. For details we refer to: https://pacechallenge.org/2019/vc Instances originate from various publicly available graph sets and reductions from other combinatorial hard problems. Details will be made public in the PACE 2019 report.