Author: Mike Adams
Date: 09:04:01 10/04/00
Go up one level in this thread
>I'm sure there is some truth to what you are saying, but if Crafty needs to >search to a greater depth to find the same tactics, isn't that a sign of some >type of inefficiency? I've noticed that some things speed up search a lot while compromising the integrity of the idea of a pure search. Move ordering doesnt do this normally. If you search every node with simple Min Max or NegaMax it will be really slow but you will see everything up to the depth you search. Now if you include alpha beta and some move ordering like order like capture it will be much quicker and just as reliable. You'll get the same depth but faster. Now say you were getting depht 5, Now you add Null Move and Futility Pruning. Both these algorithms are to put it simply ways of finding out if certain parts of the tree get lower scores and therefor are not worth searching. Now your no longer searching everything. You're making estimates. Lets say this brings you from depth 5 to depth 7. Well its no longer a pure depth 7 search as you would have had if you searched every postion. Sometimes the result of this 'estimated search' will vary from a pure search. Well here is how I look at it. In many situations your 'estimated search' is good enought and your getting 2 extra depth. In some situations you miss things that you would have seen with a pure search at an earlier depth tell later. But that can be ok. lets say a depth 5 tactic doesnt appear untill depth 7 with 'estimated search'. Well if you did a pure search you would have got depth 5 and seen it. With the 'estimated search' you got depth 7 and finnaly saw it. As long as the extra depth required is not more than the gains from the 'estimates search' you really havent lost much. And often in the cases were things take longer to find it is the case that you'll still find whatever you would have found with the full search. Now lets say a tactic should show up at depth 5 you're getting depth 7 with this 'estimated search' and you miss the tactic because you need depht 8 or 9. Then you lose but from what i have seen with Pulsar it is much better to cut off the bad lines and get the deeper search than it is to be cautious and do a pure search every time.
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