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Subject: Re: Another funky hash problem

Author: Bruce Moreland

Date: 09:36:12 08/25/99

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On August 25, 1999 at 04:56:33, Peter McKenzie wrote:

>On August 25, 1999 at 01:29:55, Bruce Moreland wrote:
>
>>
>>On August 24, 1999 at 22:02:33, James Robertson wrote:
>>
>>>I was looking at my code and noticed that I never get any cutoffs when there is
>>>no available hash move.
>>
>>I don't understand this.
>>
>>> I modifed my code a little, and it sped up, but then I
>>>noticed tactical problems;
>>
>>Are you fixing bugs or trying to make it go faster?  If you were trying to fix
>>something, why are you checking speed?
>>
>>>on a certain test position it never finds a fairly
>>>obvious move. Anyway, here is my hash code in my search function.
>>
>>You aren't sounding like someone who is in control of your code.
>
>Such a way with words :-)

Yeah, I sound pretty harsh there, although I tried to soften it in the part you
snipped.  But it's one area where I'm a little religious.  I think that it is
important to understand what software is doing, and avoid fixing bugs by
experimentation.

Especially in a chess program.  The things are so volatile because the process
takes place in a tree, which is hard to debug.  Almost any change will make a
bug disappear more often than not, meaning that you can "fix" a search bug by a
change in eval, because the tree shape changes enough that the bug doesn't
manifest.

It is possible, and I believe necessary, to understand bugs in chess programs.
It takes a lot of effort sometimes, but it pays off.

bruce



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