Author: martin fierz
Date: 05:14:38 04/11/04
Go up one level in this thread
On April 11, 2004 at 08:02:45, Tord Romstad wrote: >On April 11, 2004 at 06:33:10, Daniel Shawul wrote: > >>Hi tord >> >>what does gothmog selectivity 6 means? >>My guess is you do null_move for first 6 plies and >>static eval pruning for the rest. I mean is it like Ed's? > >No, it's not like Ed's at all. It hasn't even got anything to do with plies. >The 'selectivity' >parameter controls one of the criterions which are used to determine whether a >move >should be searched to reduced depth. The first three moves at all nodes in the >main >search are (almost) always searched to full depth. All remaining moves are >candidates >for reductions. For each move, I first check whether it is a capture, check, or >some other >kind of interesting move. If the move does not appear to be interesting at all, >I do one >final test before I decide to reduce it: > > if(History[Compress[m->from]][Compress[m->to]] < > (Nodes >> (20-EngineOptions.selectivity))) > return 1; > >As you can see, I compare the history counter of the move (i.e. the number of >times >the move has failed high in the past) to the number of nodes searched. If the >move has >almost never worked before, it is also not likely to work this time. >EngineOptions.selectivity >is a variable which contains the selectivity setting in the init file. > >When a reduced move fails low, I search it again with full depth. hi tord, don't you mean "when a reduced move fails high"? cheers martin >>I saw in gothmog's ini an option to turn off null move. >>Well does that mean selectivity 0 , which does only static eval >>pruning for the whole of the iteration depth. > >Turning null move off in the init file completely disables dynamic null move >pruning. > >>I have added static selectivity pruning in DanChess. >>This is the first time i disabled the null move code in search of other >>methods . Guess what it is not that bad! It takes around 330000 nodes to reach >>Depth 9 at the initial position for both methods. True,the static method >>sometimes make clear mistakes at positions where positional score dominates. >>The static method is only at embroic stage and that is expected any way. >>since you are more experienced than me in these method,i am hoping you will >>help me with ideas. > >I am not sure I have much more experience with you about this. I do something I >call "static null move pruning" when the remaining depth is less than 3 plies, >but >not further away from the leaves. Most of the selectivity in my search is in >the form >of extensions and reductions rather than in complete pruning of subtrees. > >Of course, I will still help you as much as I can, and I wish you good luck. >:-) > >Tord
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