Author: Tony Werten
Date: 17:43:13 02/03/01
Go up one level in this thread
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. > > > >> >>> >>>And you can _still_ turn in your assignment on time. Checkers is perfectly fine >>>to test your hypothesis. :)
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