Author: John Paul Jones
Date: 21:12:03 01/19/04
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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.
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