Author: Robert Hyatt
Date: 08:57:01 10/22/99
Go up one level in this thread
On October 22, 1999 at 11:39:28, KarinsDad wrote: >On October 22, 1999 at 09:28:21, Robert Hyatt wrote: > >>On October 22, 1999 at 00:18:37, KarinsDad wrote: >> >>>On October 21, 1999 at 22:14:01, Dave Gomboc wrote: >>> >>>>On October 21, 1999 at 17:25:32, KarinsDad wrote: >>>> >>>>>The problem is not one of how many squares can a piece move to, but rather how >>>>>many squares can a piece move to safely. Additionally, if you analyze GM games, >>>>>you will notice that a square that does not really look safe, is safe due to >>>>>some condition of the board. However, I just let the search engine take care of >>>>>that one. >>>> >>>>The problem is even bigger than this, of course. It doesn't really matter how >>>>many squares a piece can safely move to, what matters is whether it can continue >>>>to do something useful, or move to somewhere where it can do something useful. >>>> >>>>Dave >>> >>>Depending on the position, this is true. >>> >>>I look at a chess program as something with which you attempt to make moves >>>while weakening your position the least and hindering your opponent's position >>>the most. Mobility, especially in the opening and middlegame probably does that >>>right behind material and possibly piece overprotection. There are probably more >>>factors than we can even count and the weight of any given factor depends >>>heavily on the position. But, with bitboards, I think that safe square mobility >>>is something that can quickly be calculated, similar to material being quick to >>>calculate. >>> >>>I consider it a positional tactic (due to the possibilities for future good >>>moves it presents) as opposed to a material gain tactic and I consider the cost >>>to calculate it small. >>> >>>KarinsDad :) >> >> >>Here is a point to ponder: >> >>Does having lots of mobility make the position "good"? Or does a good position >>have lots of mobility? IE is mobility the 'cause' of a good position or is it >>simply the 'effect' of a good position? >> >>I believe the latter is closer to the truth. Otherwise, moves like a4 would >>be _good_ moves because they instantly improve both the real and potential >>mobility of the a1 rook. > >If I had to guess, I would say that mobility is one out of several possible >causal factors in a good position. However, it usually requires other factors >such as material equality (or material advantage), square control, king threats, >etc. In and of itself, a mobility advantage does not guarantee a good position. >Just like in and of itself, a material advantage does not guarantee a good >position. Each factor that leads to a good position is a subset of all of the >factors and it is unlikely that any one factor takes precedence over all others. >However, any given factor does not have to be present in order to have a good >position (for example, you could be down a queen and about to checkmate or you >might have only one move on the board and about to checkmate). > >However, a chess program searches the graph and keeps moves which lead to >certain criteria and discards moves which do not. The fast searchers have a >criteria of material gain (for the most part). If you could add a LOT of >evaluation factors such as square control and mobility at an inexpensive cost >similar to material gain, I think you will lead the game away from hidden >pitfalls (beyond the event horizon) for you and towards hidden pitfalls for your >opponent (on average, I doubt any algorithm could do this for all relatively >equal positions) while at the same time, searching relatively deep. > >KarinsDad :) My very first evaluation (for crafty) was material + mobility. It played _very_ poorly. I added pawn structure. It _still_ played poorly. I came to the conclusion that mobility was an effect of, and not a cause of, a good position. Some common eval 'terms' enhance mobility. Rooks on open files. Outposts. Pieces not on the edge of the board. However, I have never been happy with mobility as any sort of 'important' eval term. I use it for bishops as it handles the 'good/bad' bishop case pretty nicely. But for other pieces, I don't do mobility at all. For the queen it is _particularly_ bad.
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