Author: Uri Blass
Date: 03:47:50 01/20/04
Go up one level in this thread
On January 20, 2004 at 06:39:16, Uri Blass wrote: >On January 20, 2004 at 00:12:03, John Paul Jones wrote: > >>On January 19, 2004 at 23:23:58, Robert Hyatt wrote: >> >>>On January 19, 2004 at 19:52:36, John Paul Jones wrote: >>> >>>>On January 18, 2004 at 22:39:23, Robert Hyatt wrote: >>>> >>>>>On January 18, 2004 at 05:53:49, martin fierz wrote: >>>>> >>>>>>i just received my brand-new shredder 8. when using it for analysis in chessbase >>>>>>(which is in fact the only thing i use it for), it often gives PVs which are >>>>>>completely ridiculous - the first few moves are ok, then one side blunders a >>>>>>piece according to the PV, but the evaluation of that line doesn't show it. >>>>>>looks like there is a PV bug in shredder 8? is there any fix for this? i find it >>>>>>very annoying... >>>>>> >>>>>>cheers >>>>>> martin >>>>> >>>>> >>>>>I have heard that Shredder (and others) try to reconstruct the PV by probing the >>>>>hash table at the end of the search. This simply does not work with any degree >>>>>of accuracy. IE suppose you search and reach position A while searching the PV. >>>>> Later, at very shallow depths, you reach position A again and >>>>>overwrite it with different "best moves" depending on the depth remaining, >>>>>extensions triggered, etc. Now when you try to recover the PV from the hash >>>>>table, you get the right position A, but the wrong best move. And then the PV >>>>>looks funny. It doesn't happen every time, but if the PV is reconstructed >>>>>enough this way, it happens often enough. I tried this _years_ ago and ran into >>>>>the same problem. Never saw it in debugging. Saw it regularly when kibitzing >>>>>PVs on ICC. :) >>>>> >>>>>I now do it the correct way, backing the PV up along with the score... >>>>> >>>>>Remember that this is speculation since I have never seen Shredder's source. But >>>>>recovering the PV in this way is simply going to produce errors, and there is >>>>>nothing that can be done about it. The first move and score will be correct, of >>>>>course. But beyond that, who knows, and the farther out, the greater the >>>>>probability of a bogus move. >>>> >>>> >>>> >>>> It's halarious how you try to tell more sucessfull programmers what will and >>>>what will not work, and your program is like 200 elo points behind theirs... >>>>funny indeed! >>> >>>It's hilarious to watch you try to talk about computer chess with _no_ idea >>>of what you are talking about. :) >>> >>>Hint. There is a difference between algorithms, and implementations of >>>algorithms. Here nobody disputes that PV from hash shows bogus PVs. >>> >>>Please show another touch of brilliancy now... >> >> >>haha well atleast I admitt that I know nothing about computer chess, and don't >>go around acting like I'm a brilliant programmer when I have a Second rate >>program that nobody respects. > >Speak for yourself. >Do not speak for everybody. > >Nobody respects is simply wrong. > >Uri I can add that Bob's program is clearly better than the programs of other programmers in this discussion. The prpgrammer of Shredder does not participate in this discussion and I see no reason to assume as obvious that he cannot learn. The fact that one program is stronger does not mean that everything that it does is better. Uri
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