Author: Gordon Rattray
Date: 08:31:41 11/22/01
Go up one level in this thread
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.
Are you assuming that position (b) is included in the search of (a) or not?
Suppose (b) is seen from (a), and when initially searching at (a), (b) is
evaluated as 2.00. However, when (b) is actually reached in the game the eval
has dropped and continues to do so.
Then, analysing backwards, won't (b) be given a lower eval and since it can be
seen from (a), during the backwards analysis (a) will use this lower value and
hence it may cause a different move to be selected at (a)?
Gordon
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