Jouni wrote: ↑Sat Oct 27, 2018 8:43 am
No. 7 piece access nees all 6 piece tables and so on. So there must be more hits. Or do You think they are unnecessary?
1) Accessing a 7-men TB itself does not require presence of 6-men or lower TBs. It may be true for *generating* them, though.
2) When reaching a game position where the search tree hits a 7-men position (after some captures) then the search does not go any further beyond those nodes so even here no 6-men TBs are required.
3) When reaching a game position with less than 7 men, the engine would need the corresponding 6-men/5-men TBs etc. to play the optimal moves without search, unless these 6-men/5-men positions are contained in the 7-men TB (which they usually aren't). This will not happen with conditions that include TB adjudication, of course.
There can be a problem with positions with 7 pieces without the 6 piece tablebases because the engine may not know the correct capture that lead to win the game(there may be 2 captures when one lead to draw and one lead to win but without the 6 piece tablebases you may choose the wrong capture).
Correct, so this is another case that I forgot:
4) When reaching a game position with 7 men, the engine needs the 6-men TBs to always play the optimal move without search.
Sven Schüle (engine author: Jumbo, KnockOut, Surprise)
Sven wrote: ↑Sat Oct 27, 2018 11:09 am
1) Accessing a 7-men TB itself does not require presence of 6-men or lower TBs. It may be true for *generating* them, though.
I was thinking the same for TB-6 and TB-5, but Ronald de Man explained on this forum that TB-5 are neccesary for Syzygy-6 to work properly in all cases.
That surprises me a lot. So this means that probing the "higher" TB once is not always sufficient to obtain a perfect TB score and you may need to probe the "lower" TB as well during search?
Does someone have a link to that discussion?
Sven Schüle (engine author: Jumbo, KnockOut, Surprise)
