Transposition tables

[François Pays]

Hello,

Maybe it worth to notice that the large instance AlphaGo-zero used a transposition table.

"A transposition table was also used in the large (40 block, 40 day) instance of AlphaGo Zero."

It's very probable the Alpha-Zero inherited this transposition table as it makes very much sense in Chess and Shogi.

"Unless otherwise specified, the training and search algorithm and parameters are identical to AlphaGo Zero (29)."

The transposition table mecanism is different from the NNCache as it caches both neural network inference and current search statistics.

By the way, I noticed that the second implementation of lc0 did not make use of the Zobrist hashing. This is probably an slight oversight because we need the position hashcode at every move, for NN caching or transposition tables but also for efficiently finding repetitions. Rebuilding it from scrash again and again is much more expensive.

François

[Cezary Wagner]

For sure all chess program should use transpositions but with remember that castling is asymmetric (one middle).

Before castling is one symmetry line and it can be mirrored. After castling and pawn loose there is 4 symmetry lines (two diagonals, two middles) with pawns (two middles).

Some is for tic-tac-toe (it has 4 transpositions and 4 symmetry lines). All very good chess players understand transposition.

Good chess player not see difference in play a or h pawn and black and white at end.

Good chess player not see difference in play od symmetric position of white or black on start (before castling) - it is rare since white starts (tempo difference).

I reduce games tree 2x, 4xtimes.

Should be used at least to change black into white I think - can be used to find better moves with rotation with tradeoff speed maybe.

[Graham Jones]

Cezary,

That is not what people mean by transposition table in chess. https://chessprogramming.wikispaces.com/Transposition+Table