Author: Robert Hyatt
Date: 07:08:52 01/01/01
Go up one level in this thread
On December 31, 2000 at 19:36:05, Steve Maughan wrote: >Heiner, > >>OTOH, a general assumption underlying all this searching business is >>that deeper searches generally produce better (more accurate) results. >>I.e. if we alrady have an even more correct result than the one the normal >>search would yield, we tend to to happily accept that, and we do expect >>to improve by this. Right? > >Yes. This is why when one raises alpha one must also cut the PV. What is >really happening is the deeper search info is being graphted onto the search. > This statement is still simply incorrect. You don't _touch_ the PV. The issue is that you are searching, and someone whispers in your ear "Hey, your alpha value is -1.2... I actually have searched this position before and I proved that the score is actually no worse than -1.0... so change your alpha and keep searching." You don't affect the PV, or anything else, other than make the search more efficient. If the new alpha value is >= your old beta value, you should have _already_ bailed out with a fail high. If your new beta value is lower than your current alpha value, you should have already bailed out with a fail low. I don't understand the concept of "cutting off the PV"... The PV is backed up from below, not built as you search downward... >>Of course you could restrict TT hits to only occur if the draft exactly >>matches the depth. I suspect that would reduce the benefit from the TT >>in most cases, and quite drastically so in some cases (like the famous Fine >70). > >Yes I'm sure there's scope for fiddling when Depth = Hash Depth. > >>Do you really exclude TT entries with a larger draft? > >I'm not sure what you mean. > >I think I'm finally started to get my head rpound this issue - it's being vexing >me for days!! > >Regards, > >Steve
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