Author: Uri Blass
Date: 22:11:20 11/22/01
Go up one level in this thread
On November 22, 2001 at 19:45:56, Robert Hyatt wrote:
>On November 22, 2001 at 16:00:43, Mike S. 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? (...)
>>
>>>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.
>>
>>I know what you mean, but I have seen that engines behave very differently at
>>this. Maybe it's because they do the replacement of hash entries in different
>>ways (I suspect some remove entries although there's still a lot of free space
>>in the tables, because I usually stay only for some seconds on a position), or
>>maybe some are especially equipped for that analysis method.
>
>Doesn't matter, when you think about the math. Either you keep all the
>positions from the first searches, which means newer searches (going backward)
>will have no table space to write into, or vice-versa...
It is also possible to keep always the scores of the position from the game and
the depth so the program does not need to analyze game positions when the
remaining depth is smaller when it goes backward.
In this case if there is a long forced line in the game that is too deep for the
program then the program may analyze better when you go backward.
Uri
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