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Subject: Re: Parallel algorithms in chess programming

Author: Robert Hyatt

Date: 20:06:55 04/16/01

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On April 16, 2001 at 22:53:34, Eugene Nalimov wrote:

>On April 16, 2001 at 22:07:10, Robert Hyatt wrote:
>>On April 16, 2001 at 18:15:52, Dieter Buerssner wrote:
>>>In a different discussion, Vincent wrote the following:
>>>>It is not difficult to implement the form of parallellism as used by
>>>>Rudolf. Invented by a frenchman who couldn't spell a word english and
>>>>who wrote an impossible article for JICCA (did anyone proofread it at
>>>>the time as i'm pretty sure they didn't get his parallel idea?).
>>>>At the time when i read the article i was pathetically laughing about it
>>>>actually as i also didn't get the idea of the frenchman. But it appears
>>>>everyone who can make a chessprogram work under win2000 can also get
>>>>within an afternoon his program parallel to work. Then some debugging
>>>>and a day later it works cool.
>>>I'd be very interested in this algorithm, that can be implemented at an
>>>afternoon :-)
>>>Could you point elaborate on this.
>>>BTW. In Paderborn, Roland Pfister also told me, that he knows this from Rudolf
>>>Huber, and he even started to explain it to me. Somhow, we (or me) got
>>>distracted, and I cannot remember the essential things.
>>>What I remember is, that the time consuming work, of making your
>>>search/evaluation routines free from all those global variables is not needed.
>>Global variables will _always_ be a problem.  Unless you avoid threads
>>altogether and use separate processes.  But then you incur other penalties
>>you have to solve...
>Visual C allows you to declare the global variable as "thread-specific", i.e.
>each thread will have its own copy of the variable. Compiler generates special
>code to access such a variables.

Many machines have a variant of this.  On the Cray, we had global variables
in FORTRAN via a "common" statement.  They added "task common" which were
global but thread-specific.

I do the same thing via pointers in normal C.  A thread-specific (local) pointer
that points to a global area that is allocated to a specific thread for its
exclusive use...

But any such thing causes syntacical changes and lots of debugging...

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