Author: Robert Hyatt
Date: 19:01:50 10/18/99
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On October 18, 1999 at 21:17:29, William Bryant wrote: >I may not ask this question right, so allow me the luxury of a long winded >question to try and explain the question completely. > >When starting a new iteration, the PV holds the best moves searched to the depth >of n-1 (the previous depth). These moves form the far left (or far right?) of >the search tree and make the first moves searched. Now the question, since >these moves have already been searched, is there any point in stopping along the >way and doing a null move until this line has been extended initially to the new >depth. IE the first leaf evaluated should be at the end of the old pv, should >it not. > >My Null move code starts checking null moves while depth is sufficient. >Therefore, it will start null moves as soon as the first few moves of the pv >have been made on the way to the first leaf. I empirically think that this will >simply waste time because this line has already been searched, and that null >moves should be postponed until after the first leaf has been searched or until >the tree has been extended initially down the first branch following the pv to >it's first. > >Am I close? Is there any advantage in doing the null moves while still >following the pv to the first leaf? > >William >wbryant@ix.netcom.com > >//my code idea goes like this > >if (pv_move) > do_Null = false; > >pv_move is set to false as soon as search at any iteration moves beyond the >bestmove phase and generates moves for the ply. I used to do similar things years ago... but I found that trying null-moves _everywhere_ helps in a lot of cases, hurts in only a few cases, and overall is better. Not to mention making the code simpler, using one less register to pass that flag from one Search() call to another, etc... However, that was _my_ results. That doesn't mean it will be _your_ results. You ought to try it both ways. BTW are you doing the hash table trick that lets you avoid null-move searches in the right place? It effectively prevents trying null-moves in the PV positions you gave anyway...
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