Author: Robert Hyatt
Date: 07:53:57 11/23/01
Go up one level in this thread
On November 23, 2001 at 01:11:20, Uri Blass wrote:
>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
What is "forced" to you and what is "forced" to the engine are two different
things. Which is what makes this a problem...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.