What do you think the average would be?
No idea, I don't know what kind data OP stores (mostly few pieces? or lots of pieces? etc). You can probably tailor your format if you have more insights. But no matter what, you can always have some gain compared to a naive approach. I would say storing a pos for each piece might be naive, since there are a lot of rules that allows you to exploit things
My 248 bit was the absolute worst, when you have 8 promotions on board and lost none of (non-pawn) pieces. For example the initial board would be about 190 bits as well and most would be lower as you capture pieces. I think that would be a worst case for you as well but I don't get this part
If a pawn is promoted (and there are more than than the starting number of the piece it was promoted into) repeat the position of the piece it was promoted into
You mean you first need to tell the position of the piece it is promoted to and then another position for the position of the pawn (now promoted)? Then you have a pretty bad worst case as well
But you are right, I made an overcomplicated solution. Here is a simpler one that should perform better https://news.ycombinator.com/item?id=39066557
My 248 bit was the absolute worst, when you have 8 promotions on board and lost none of (non-pawn) pieces. For example the initial board would be about 190 bits as well and most would be lower as you capture pieces. I think that would be a worst case for you as well but I don't get this part
You mean you first need to tell the position of the piece it is promoted to and then another position for the position of the pawn (now promoted)? Then you have a pretty bad worst case as wellBut you are right, I made an overcomplicated solution. Here is a simpler one that should perform better https://news.ycombinator.com/item?id=39066557