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Subject: Re: Time control legend

Author: Dave Gomboc

Date: 08:46:47 05/16/98

Go up one level in this thread

On May 16, 1998 at 10:27:28, Don Dailey wrote:

>>>>>I dunno why Rebel+Fritz+genius and some others
>>>>>are so horrible in these exchanges, but my first guess was piece square
>>>>>tables. Now i say: perhaps mobility is a reason too.
>>>>>The common thing of all these programs compared to Crafty, Zarkov, Diep
>>>>>and some others is that they lack mobility terms.

For the record, the above was written by Vincent Diepeeven, not myself.

>I know this is not correct for Genius.  One of the few things Richard
>Lang ever "gave up" about his program was some details on the mobility.
>He even does queen mobility.   Of course this was a few years back,
>it's possible he stopped using mobility.
>I am curious about different implementations of mobility.  Here is a
>rundown of ways I've done BISHOP mobility through the years:
>1) Simple square count method (legal moves)
>2) Simple square count where I pretend only pawns on board.
>3) Combinations of 1 and 2 folded together.
>4) Method 2 with table.
>5) Method 1 or 2 but pawn attacked sqaures count less or not at all.
>6) Not at all.
>Method 4 is something I found useful.  I count the squares but use the
>count to index a table.  The table is designed to emphasize "minimal
>mobility",  I consider it more important to go from zero to 5 sqaures
>that to go from 5 to 10.  This helps a lot in positions where you choose
>to "improve" a well developed bishop when you should be doing more
>constructive things.  I don't have proof this is any better, it's a seat
>of the pants thing from observing lot's of games.
>I think method 5 is the very best, but my programs found it quite
>expensive to compute, others might do better.  I may eventually
>implement this in Cilkchess because with bit boards it will probably
>be fairly cheap.
>Method 3 seems like an improvement over either 1 or 2, but I believe
>method 1 is the least good.  But in some positions it makes more sense.
>Nothing is completely ideal for every situation.  So I generally give
>more weight to pawn considerations.  I also had a program that didn't
>count squares where pieces blocked it but skipped over them until it
>ran into a pawn.
>As far as rook mobility is concerned, I believe it's more important
>to judge open and half open files.  I think rank mobility is useful
>if the weight is kept low, the same probably applied to file mobility
>but again, prime consideration is openness.   One consideration is
>attacking enemy pawns.  Is it mobility restricting, or is it a good
>thing?  The answer is both!  I try to focus on what I'm measuring,
>and I'm not measuring rook bonuses for attacking pawns.  Since I'm
>measuring mobility, I oount pawns that can be captured as mobile
>squares but don't count any farther.  I have a separate term for
>various attacks on undefended pawns.
>Method 6, I don't know about.  Right now cilkchess using this method
>and I feel like I have problems too often with bishops. I have some
>static" terms that judge a bishop's worth like pawn counts on certain
>color squares and a term that attempts to measure a bad bishops
>which I have mixed feelings about.   Also a table with weak weights
>to get the bishops out to the center a little.  Sometimes though,
>the bishops get confused about where they belong.
>- Don

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