During our work, we have collected and/or developed several suites of test instances for different optimization problems: they are made freely available to they scientific community, in order to stimulate the research on computationally effective algorithms.
If feel you have something to add, either instances/generators or links to other interesting sites, please contact us.
For some of these problems we also distribute solvers; please check our Software page.
Multicommodity Min Cost Flow problems.
Single-commodity Min Cost Flow problems.