Author: Robert Hyatt
Date: 07:52:58 11/23/01
Go up one level in this thread
On November 22, 2001 at 23:16:41, Dave Gomboc wrote:
>On November 22, 2001 at 09:42:36, Robert Hyatt wrote:
>
>>On November 22, 2001 at 05:27:05, Gordon Rattray wrote:
>>
>>>The Fritz GUI analyses games ("Full Analysis") by starting at the end of the
>>>game and retracting moves. How does this compare to going forwards? Does it
>>>produce better results?
>>>
>>>I think this issue has been discussed before, but my search has failed to find
>>>anything. Please feel free to forward me a past link if appropriate.
>>>
>>>Gordon
>>
>>
>>Here is the idea...
>>
>>If you start at the end of the game, you load the hash table with stuff
>>that will help as you search at earlier moves... with the "idea" that
>>earlier analysis will be more accurate since it will have access to these
>>scores.
>>
>>It doesn't work however.
>>
>>IE pick three points in the game, (a) where a key mistake is made, (b) a
>>position further into the game, and (c) a position near the end where the
>>program can see that it is lost. As you search backward, when you reach
>>(b) the search might well _still_ see that it is lost, because of the persistent
>>hash entries that help. But when you back up past (b) eventually the
>>hash entries get replaced, and you "lose the key scores". You don't find the
>>_real_ place where you screwed up (a), instead the score seems to drop at
>>(b) which is the wrong place.
>>
>>Since neither way finds the actual mistake, I don't like the back-to-front
>>approach because if you do search front to back you will find the "mistake"
>>at a different place, which is nothing more than confusing.
>
>Overall, the analysis is more accurate when it is performed from back to front.
>Sure, there are still mistakes, but that's life.
>
>You used to recommend the back-to-front order yourself. In fact, I remember you
>criticising Fritz once for doing it in the forward direction. :-)
>
>Dave
I don't remember critizing Fritz, but whether I did or not, I decided to try
it and didn't like it. I want the program to be as consistent as possible when
it gives me analysis. If it can _prove_ that my move was worse then I want it
to say so. But if it can't, I don't want it to say so just because it luckily
kept something critical in the hash.
IE if the _real_ problem is at move (A) and the program can't see it is in
trouble until move (B), then Crafty will report the problem at B every time,
until the hardware gets faster and then it will report it at B-1, etc...
With the reverse annotation idea, it will report it at random locations between
(b) and (a) which I simply didn't like. Change the hash size (bigger or
smaller) and the point where it spots the problem changes.
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