multi-dimensional knapsack problem (MKP) instance generation

Hi,

I am interested in developing heuristic algorithms (e.g., GA) for
solving large-scale MKPs, but found little public problem instances of
large size for benchmark purpose. Those included in ORLIB are usually
small. Anyone knows where to find such info.?

Another question is how to generate large-sized problem instances with
known optimal value. Maybe I did not do enough literature review, but
does there exist a mechanism to construct such a problem instance,
instead of generating it randomly and getting bounds by using linear
programming software which is not feasible for large size problems.

Thanks,
Ian
.