TalkChess.com

[H.G.Muller]

I am not sure what problem you try to solve here. In a collection of games almost all positions will occur in only a single game. So there is not a huge gain in terms of number of positions when you cllapse multiply occurring (opening) positions to one. If combining involves some overhead, like extra pointers, you quickly lose more than you gain.

If you want to store PGN that includes comments or recursive variations, you have the additional problem that games with the same initial moves might have different comments, or ar annotated with different variations. So it is crucial to know how you want to handle comments and variations. Is this for an application where you can simply strip them? Are they stored separately from the moves?