Author: Alvaro Jose Povoa Cardoso
Date: 01:50:34 02/04/01
Go up one level in this thread
On February 03, 2001 at 22:45:07, Robert Hyatt wrote: >On February 03, 2001 at 20:43:13, Tony Werten wrote: > >>On February 03, 2001 at 18:33:28, Robert Hyatt wrote: >> >>>On February 03, 2001 at 05:53:20, Tony Werten wrote: >>> >>>>On February 02, 2001 at 21:33:10, Robert Hyatt wrote: >>>> >>>>>On February 02, 2001 at 14:42:23, Alvaro Jose Povoa Cardoso wrote: >>>>> >>>>>>On February 01, 2001 at 18:37:48, Robert Hyatt wrote: >>>>>> >>>>>>>On February 01, 2001 at 16:27:29, Tony Werten wrote: >>>>>>> >>>>>>>>On February 01, 2001 at 14:19:25, Alvaro Jose Povoa Cardoso wrote: >>>>>>>> >>>>>>>>>Does any one tried to use just Upperbounds and Lowerbounds in hashing, ignoring >>>>>>>>>ExactScore entries? >>>>>>>>>My question has to do with the fact that if we use ExactScores we don´t get long >>>>>>>>>PVs to feed in the next iteration, even if we extend PVs from hash. >>>>>>>>>My testing shows that if we do not use ExactScore entries in the hash table, we >>>>>>>>>end up with very long PVs that can be fed into the next iteration in order to >>>>>>>>>aproximate the minimal tree. After all, ExactScores are rare compared to >>>>>>>>>Upperbounds and Lowerbounds. >>>>>>>>> >>>>>>>>>Can someone comment on this? >>>>>>>> >>>>>>>>One of us is missing something. The PV is always exact. If you don't store >>>>>>>>exact, you don't have a pv. I don't know what you get from the hashtable, but it >>>>>>>>isn't a PV. >>>>>>>> >>>>>>>>I take my PV from hashtable and I (almost) always get a long pv, at least as >>>>>>>>long as the search depth. >>>>>>>> >>>>>>>>Tony >>>>>>>> >>>>>>>>> >>>>>>>>>Thank you >>>>>>>>>Alvaro Cardoso >>>>>>> >>>>>>> >>>>>>>He is talking (I think) about a PV that is cut short when you get an EXACT >>>>>>>hash hit. IE in crafty, where a PV ends with <HT> which sometimes happens >>>>>>>at ply=2/3/4 and results in a very short PV. I use internal iterative deepening >>>>>>>to help search around this the next iteration, however.. >>>>>> >>>>>> >>>>>>That is exactly what I was talking about. When I get an EXACT hash hit the PV is >>>>>>cut short, and extending it from the hash table doesn't help much, I just get >>>>>>1-3 moves from the hash, perhaps there is something wrong with my program. >>>>>>Also, and in response to Dr. Robert Hyatt, I can´t execute the assignment >>>>>>because my program is the portuguese version of checkers. I hope you don't mind >>>>>>if I ask questions not related to the game of chess. >>>>>> >>>>>>Thank you >>>>>>Alvaro Cardoso >>>>> >>>>>That is a perfectly normal problem. My PV is often shorter than it should >>>>>be due to an EXACT hash hit. Nothing you can do about it, not that there >>>>>is anything wrong with it. >>>> >>>>I still don't get how you can have a short pv if you have a exact hashhit. >>>> >>>>Maybe run a test where you add in your pv, the bounds it got. My guess is you're >>>>last move is a BELOW_ALFA hit. ( That was a problem I had before ) >>>>It was caused because I raised alfa after nullmove, sometimes making it the best >>>>score and having a bogus best_move which couldn't be found in hashtable. >>>> >>>>cheers, >>>> >>>>Tony >>> >>>It happens all the time. You get an EXACT hash hit while searching the PV, >>>so you stop and use that score instantly. How can you fill in the _rest_ of >>>the PV moves since you didn't search any deeper. I see this so often that I >>>eventually added the <HT> indicator to the PV to let everyone know it really >>>should be longer but was cut short by an EXACT hash hit. >>> >>>If you never get a short PV, you have something broken somewhere.. >> >>But if you get a <HT> you must have searched it the previous ply, so it's still >>in your tables ? Or you've searched it this ply and you should not have >>overwritten it. ( or you have something broken somewhere .. ) >> >>Tony >> >>PS very strange strange that if you don't get an error you must have something >>broken. > > >No, because this is _not_ an error. It is a well-known occurrence when you >hash. > >The <HT> can come from any of the following: > >1. deep ponder search where the opponent made a different move than you >expected. IE You were expecting him to play Nc3 and your PV was e5 Re1. >But instead, he played Re1. After you search e5 and Nc3, you get the same >position exactly and search no deeper. > >2. Same as (1) but from the current search. It is possible to reach >position X in more than one way, and one of those ways could have extended >the tree deeper than the one you are on now, which will give you a <HT> >score that is exact. > >3. Something left over from an old search. > >4. something from position learning if you have that. > >If you don't get an EXACT hit on your PV from time to time, as I said before, >something is wrong. Because _anytime_ you get an EXACT hit, you don't search >any deeper. How do you fill in the PV below that point? > If I'm not mistaken you said _internal_iterative_deepening_ can be used to fill the PV below this point. Can you explain the details, you see I'm a novice on this things. Alvaro Cardoso >>>>>And you can _still_ turn in your assignment on time. Checkers is perfectly fine >>>>>to test your hypothesis. :)
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