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Subject: Re: Chess program improvement project (copy at Winboard::Programming)

Author: Dann Corbit

Date: 21:41:55 03/06/06

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On March 07, 2006 at 00:34:48, Stuart Cracraft wrote:

>On March 07, 2006 at 00:31:45, Dann Corbit wrote:
>
>>On March 07, 2006 at 00:27:43, Stuart Cracraft wrote:
>>[snip]
>>>Very interesting indeed. A clever test.
>>>
>>>If one's results do not rotate approximately as described
>>>for the four positions and you say the evaluation is an
>>>issue, what kinds of evaluation issues have you seen that
>>>could explain it?!?
>>
>>The most common thing that I see is something that is good for white being
>>counted as positive for black also on the evaluation.  Often, when we are
>>writing the eval, we are thinking from the perspective of white. And so if we
>>are not very careful, we may invert the sign of some evaluation component and
>>count something that is good for white as something that is good for black (or
>>vice versa, though the reverse is seen less often for some reason).
>>
>>There are, of course, many other possible causes besides that.
>
>A good point. I try to avoid that by always doing things from the
>side on move, almost always. There are a few in there however with
>respect to white and black specifically, but they are then folded
>together with the stm variable and stm^1 which translate to white/black
>or black/white depending on who's on move. I could try this: rerun
>your rotation test with successively less in the evaluation table
>until nothing but material and see what happens.

Right.  If you have divided off the eval components, you could binary search
until you find the problem component.

Now, we do not know for sure that it is an eval sign problem.  However, the fact
that the records are similar in pairs makes it very suspicious.




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