Re: [Boost-users] number cores / cpu

Subject: Re: [Boost-users] number cores / cpu
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2010-08-23 19:57:12

On Mon, Aug 23, 2010 at 8:32 AM, Jeff Flinn
<TriumphSprint2000_at_[hidden]> wrote:
> Mathias Gaunard wrote:
>>
>> On 23/08/10 15:00, Jeff Flinn wrote:
>>
>>> Just beware, IIUC, that the returned count includes hyperthreads(intel).
>>> Which if used to set up a thread pool may lead to surprisingly poor
>>> performance.
>>
>> What makes you think so?
>
> Experience with our application using 2 calculation-threads on a
> hyperthreaded dual core was 80% faster than using 4 calculation-threads.
>
> What makes you ask? :-)

I also have to pipe in on this, I have learned to truly *hate* the
Intel hyper-threading, it hobbles my threaded programs severely,
severely enough that I put in an override configuration option so the
user can specify how many *real* cores they have...

I still know not the purpose of them, other then to slow everything down...

(Well yes I do know the purpose, but only in poorly written threaded
apps anyway.)