Author: Anthony Cozzie
Date: 07:50:53 01/15/04
Go up one level in this thread
On January 15, 2004 at 07:48:42, Matthias Gemuh wrote: >On January 15, 2004 at 06:59:15, Volker Böhm wrote: > >>On January 14, 2004 at 15:44:56, Matthias Gemuh wrote: >> >>> >>> >>>Does it make sense to use PVS algorithm to implement QSearch ? >>>It does not seem to help my engine. >>> >>>/Matthias. >> >>PVS is good if >> >>1. there are many alternative nodes (never got good results in my connect-4 game >>with 7 moves max. at one ply) >>2. the move ordering is good >>3. you can narrow the window greatly compared with the usually arising >>position-values in a search. >> >>In QSearch: >> >>1. Depends a little bit what nodes you are searching. If you only search "good" >>hits selected by SEE its verry narrow. If you are searching check-moves too it´s >>wider. You can consider PVS if searching check-moves tool. >>2. Move ordering in QSearch is seldom good. You haven´t got a PV and seldom >>usefull hash-moves. If you turn off SEE for "good hit-moves" the ordering is too >>bad for PVS >>3. I´am staring a new search with a windows of -30cp .. +30cp around the search >>result of iteration-1. The window in QSearch is often of witdh 0, but verry >>seldom of width > 60cp (only if I´ve got fail-high or fail-low against the >>initial window). The results of a QSearch differ greatly as they are hitting >>material. The least effective hit move gets +100cp. Conclusion: the window is >>allready verry narrow compared to the results of QSearch calls. >> >>Conclusion: >>Don´t use PVS in QSearch. >> >>Greetings Mangar > > > > >Thanks for this elaborate answer. >BTW, in QSearch I also generate moves for > >1) all passed pawns >2) all attacked pieces moving to unattacked empty squares > >/Matthias. OK, this seems very strange to me. If your eval is < alpha, how is moving an attacked piece going to increase it? The only way this makes sense is to never stand pat in q search. Tord's idea _sort of_ makes sense (I have seen similar horizon problems in Zappa) but this will make your qsearch 99.9% of all nodes! anthony
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