Author: Robert Hyatt
Date: 15:33:28 02/03/01
Go up one level in this thread
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.. > >> >>And you can _still_ turn in your assignment on time. Checkers is perfectly fine >>to test your hypothesis. :)
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