[rules-users] Drools Planner for purchasing optimization - good fit for problem?

I'm trying to understand whether Drools Planner is a good fit for a purchasing optimization problem. The problem is something like this: there are X different items, each of which can be purchased from Y different vendors at different prices. The objective variable/function to minimize is the total amount purchased (sum(qty_i * price_i)). Some vendor prices are conditional - only valid if you purchase more than some minimum threshold, or if you purchase more than some total quantity from that vendor. There are some additional constraints like dual-sourcing - for some item x_i, exactly two vendors must be selected. I feel like you *could* probably solve this problem in Drools Planner, but I'm not sure if it's the best way, or if a more traditional solver approach would be better. It feels more like a linear programming problem at its core, and I'm having a hard time figuring out where the boundary is - what kind of constraint would make the problem "non-convex" or "non-smooth" to the point where a local search (tabu, evolutionary etc.) is required? Thanks for any help you can give. --Bill