Remove call to System.gc in solver
I did some performance tests with the partial weighted maxsat solver called in many (up to 150) threads. After a while, tens of threads stuck in the call to "System.gc" in the class "org.sat4j.minisat.core.Solver", method "reduceDB()". This was a major performance bottleneck. I downloaded the source, removed the call to "System.gc", compiled the sat4j-core and started the performance test again. The bottleneck was gone.
I think this call to System.gc should be removed. If there is really a need for this call, it could be made configurable (via an API call), so that it can be switched off if sat4j is used in multithreaded applications.