[Haskell-cafe] Substring replacements

Branimir Maksimovic bmaxa at hotmail.com
Sat Dec 17 06:18:40 EST 2005

>From: Bulat Ziganshin <bulatz at HotPOP.com>
>Reply-To: Bulat Ziganshin <bulatz at HotPOP.com>
>To: "Branimir Maksimovic" <bmaxa at hotmail.com>
>CC: daniel.is.fischer at web.de, Haskell-Cafe at haskell.org
>Subject: Re[2]: [Haskell-cafe] Substring replacements
>Date: Fri, 16 Dec 2005 16:51:32 +0300
>Hello Branimir,
>Friday, December 16, 2005, 5:36:47 AM, you wrote:
>BM> I've also performed tests on dual Xeon linux box and results are
>just to let you know - GHC don't uses pentium4 hyperthreading,
>multiple cpus or multiple cores in these tests
Oh yes it does. I clearly see multiple threads that take unequal percentage 
each virtual CPU. I guess that other thread is garbage collector
thread. In case of hyperthreading, speed is gained by reduced memory
latency by 30-60 %

>only way to make ghc using multiple processors is to use 6.5 beta
>version, compile with "-smp" and explicitly fork several threads

This is not the case as I see. On windows search replace test programs
spawn 3 threads and on linux I'm not sure, but I've checked program that 
calls Haskell
from C++ and GHC spawns additional thread, which is not my thread, that
also performs something constantly, and I didn't spawn any thread
from Haskell.
So hyperthreading helps as it helps to optimise when several threads
accesses memory as is in this test case.
I can't see any other explanation why KMP search is
slower on AMD 20% , but faster on Intel 30%, then straightforward search
with my test.

Greetings, Bane.

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