On Tue, Oct 12, 2004 at 12:18:14PM +0800, L WK wrote:
>>for sure.
>> mpirun h -c 2 program
>>you might get ~20% faster if you're lucky.
>Thanks. It's said that to make use of hyperthread tech., you should have
>some threads running inside your process, isn'it? Anyway, I have check this
you need more than 1 thread or more than 1 process, yes. Otherwise how
are you going to make use of your "extra" cpu?
>But find that it just got a little bit faster than that running on a
>non-hyperthreading-architecture system
"a little" is about all you can expect. HT is just faking a 2nd cpu
after all. you will never get 2x faster with HT. HT means you get
slightly better usage out of your existing single cpu, assuming that
the functional units (adders, multipliers, TLB etc) aren't maxed out
already. For example, a super-efficient SSE/MMX code would see almost
no speedup from HT.
10-20% speedup would be usual for "normal" code.
This assumes that you don't introduce inefficiencies of the same order
by breaking up your problem into 2 smaller parts (eg. crappy load
balancing or becoming communication dominated).
cheers,
robin
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