What is the problem with a high branching factor? You can search less deep in a given time, of course, but that also holds for any opponent.
I was surprised by just how shocking slow it became.
With alpha-beta the EBF only grows as the square root of the typical number of moves. So even if the latter is 6 times higher, the EBF would only go up by a factor 2.5.
The square root growth is a theoretical value, and while it may be commonly achieved, it is certainly not guaranteed. What I suspect is happening is this. The board is very large, the armies start far apart, and no additional evaluation parameters have been added. So I suspect that there are just a lot of moves where the evaluation is the same so we get way less beta cut-offs.
I was surprised by just how shocking slow it became.
The square root growth is a theoretical value, and while it may be commonly achieved, it is certainly not guaranteed. What I suspect is happening is this. The board is very large, the armies start far apart, and no additional evaluation parameters have been added. So I suspect that there are just a lot of moves where the evaluation is the same so we get way less beta cut-offs.