Separating the Valve Groups

Making the two 6-pulse valves groups as 2 SSN groups has the advantage that memory requirements are minimized because there are only 2⁶=64 permutations per group instead of 2¹²=4096 for one 12-valve group.

It may allow the simulation to run inside the L1 or L2 cache of microprocessors so it may speed up the simulation even if we now have 11 SSN nodes.