Author: Amir Ban
Date: 13:53:28 11/16/98
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On November 16, 1998 at 14:36:32, Robert Hyatt wrote: >On November 16, 1998 at 12:09:33, Amir Ban wrote: > >>> >> >>I don't think so. This one is not a "nonsense" PV. It's genuine and needs an >>explanation. >> >>Amir > >Here's a very precise question for you: Have you *ever* had Junior analyzing >games where others could see it's output? An example: I often have Crafty >give online analysis on ICC when GM's are playing in major tournaments. And >in *every* game, someone will do this: Take a PV returned by a 13 ply search, >play the moves on a "scratch" board, then say "hey all you guys that were >amazed that Crafty had predicted all of the last 30 moves but one, look at >this position after it's analysis." And invariable there will be some funny >stuff at the end of the PV that produces a position that is quite questionable >when looked at in that light. > >So, the point is, then, is it really important to look at moves further down >the PV and try to justify *them* as well? Or is the move played at the root >the place where we want the most accuracy? I'd *love* to do 13 ply searches >and produce 16 move PV's where every move was of GM caliber. But I know that >the root move will be *very* good. The second move a little worse because it >is a 12 ply move... the third move a little worse still... etc... I often >see oddball moves near the end of a PV, when the goal is to simply prevent some >"threat" that I analyze from happening (IE Qa2 to prevent your playing Rb2, even >though Rb2 is totally unimportant while Qa2 puts the queen in a horrible >position.) I fix what I can, but I still see this. In fact, I see this in >*all* programs that I watch where the operator will cut/paste analysis and send >it to ICC... > >I'm much less worried about what's happening at the *end* of DB's PV's than >I am interested in what is happening at the *front*. I'm sure you must have >seen positions where there was a sequence in the PV that goes like this: > >1. Nc3 Bf2+ Kh1 or 1. Kh1 Bf2 Nc3. Same position, right? Not quite. That >+ drives the PV one move deeper along that path, so if there is something I can >do deep in the tree I don't move my king, knowing he won't check to extend my >search so that I can see the result, or if it is something bad, I'll move my >king so he can't check me and drive the search deep enough where I see the bad >thing. Horizon gets us all from time to time, still. Lots of reasons to >explain an unexpected queen move. From horizon, to eval quirk (defending >against a useless threat) to a parallel search anomaly to a hashing anomaly to >an outright bug. But I don't see why "it needs an explanation." Maybe we are >curious and we have to figure out why... but I certainly don't intend to spend >the rest of my days explaining every odd thing my program does... otherwise I >won't ever get anything else done, because it does *lots* of odd things still. I am afraid that once again you plunge into a long and irrelevant monologue because you do not take a few seconds to check what it is I'm asking and why. Amir
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