Author: Uri Blass
Date: 01:49:06 10/20/04
Go up one level in this thread
On October 20, 2004 at 02:21:26, martin fierz wrote: >On October 19, 2004 at 10:34:39, Tord Romstad wrote: > >>On October 19, 2004 at 04:15:19, martin fierz wrote: >> >>>On October 18, 2004 at 22:10:48, Zach Wegner wrote: >>> >>>>Going back into the main search is the cheap way out, IMO. >>> >>>i disagree. going back into the main search is the right way out IMO. let's say >>>you duplicate your code in the qsearch for the case you're in check as you >>>suggest. then you change something in the way you handle in-checks. => you have >>>to change it in two places. a very bad idea... >> >>I agree with Zach here. There is really not a lot of code that needs to be >>duplicated in the qsearch anyway. In both of my engines, the only special >>code for handling situations where the side to move is in check in the >>qsearch is that all legal moves are generated (rather than just captures, >>promotions and checks), and that returning a stand pat score is not allowed. >> >>>the speed gain you get for your version is probably tiny - i admit that it will >>>be faster. >> >>The speed gain could be quite big (at least in some positions) for engines >>which extend single replies to checks. If you call the main search from the >>qsearch when the side to move is in check, there is a risk that there is >>only a single legal move, and that this move will be extended. This means >>that you will stay in the main search for yet another ply, and search >>all moves rather than just captures for one more ply _after_ the check >>evasion. This can be quite expensive. It will probably help you find >>some tactics more quickly, but I doubt that it is worth the cost. > >i do extend single replies, but in fact my feeling is that the behavior you >described is a feature and not a bug :-) >perhaps you're right though and i should give it a try. > >cheers > martin I do not let my qsearch call the main search after checks because I do not want my qsearch to search every sequence of check escape check escape,.... The number of these sequences(even after pruning by alpha beta) can be easily more than 10^9 in some positions and the search will explode. Uri
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