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Subject: Re: Hammer info. And som SMP musings.

Author: Tom Kerrigan

Date: 10:50:02 03/26/02

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On March 26, 2002 at 12:01:30, Vincent Diepeveen wrote:

>If you manage to turn on SMT at the P4 chip, sure :)
>Intel has put on its homepage however that 'currently it is turned
>off at the chip'.
>hehehehehehe

I don't see why you're laughing, because you pretty much just admitted that
you're an idiot. How can you go around declaring that HyperThreading is a load
of marketing crap that yields no performance gain when you have absolutely NO
data on the issue?

>that in DIEP i can do (multiprocessing)
>if( quickboard[sq_d3] == whitebishop )
>where with multithreading you always need indirection:
>if( thisthread->quickboard[sq_d3] == whitebishop )
>SEE WHAT I MEAN?

This is a chess-specific issue, not an issue with threading in general, and it's
not even a performance problem depending on the addressing modes that your
processor supports.

But it doesn't even matter, because the P4 exposes itself as two logical
processors, so you can just run two Diep processes on it. No need for threading.
You would have known this if you had paid attention to my previous posts. Now
you just look like an idiot.

>>I can do math, but have you taken a computer organization class? It doesn't
>>matter how big your stupid data structures are, the only thing that matters is
>>how big your working set is.
>I'm not the fool here Tom, please see above. You forget an overhead
>which is pretty big and causes processors like the P4 to be not happy.

You are the fool, because you can't follow a simple argument about working sets.
What does your indirection argument have to do with cache thrashing??

>>Really, how about you give us some measurements? Oh, right, you don't have any.
>>You make these numbers up.
>I'm at least measuring things where possible. You have had 1 theoretic
>class where probably teachers told you thread = process. Well it isn't.

Well, if you're measuring things where possible, then you should have no problem
telling us EXACTLY how many instructions/clock Diep retires. So...?

>In fact if you read in the API from M$ the first sentence then it will
>show you even more trouble when multithreading under windows. It says
>that when a thread is doing graphics, that all other threads are
>getting blocked when one of the threads is performing work.

Then don't do graphics with your chess threads.

-Tom



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