Author: Matthias Gemuh
Date: 04:48:42 01/15/04
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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.
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