Re: [amibroker] Re: Dual-core vs. quad-core, AmiBroker Email List Archive

I?m not sure why that would be the case since I can involve multiple machines over a network as opposed to local cpu?s / cores with fairly low overhead making it definitely worthwhile ?

From: amibroker@xxxxxxxxxxxxxxx [mailto:amibroker@xxxxxxxxxxxxxxx] On Behalf Of markhoff
Sent: Monday, May 12, 2008 4:31 PM
To: amibroker@xxxxxxxxxxxxxxx
Subject: [amibroker] Re: Dual-core vs. quad-core

If you have a runtime penalty when running 2 independent AB jobs on a
Core Duo CPU it might be caused by too less memory (swapping to disk)
or other tasks which are also running (e.g. a web browser, audio
streamer or whatever). You can check this with a process explorer
which shows each tasks CPU utilisation. Similar, 4 AB jobs on a Core
Quad should have nearly no penalty in runtime.

Tomasz stated that multi-thread optimization does not scale good with
the CPU number, but it is not clear to me why this is the case. In my
understanding, AA optimization is a sequential process of running the
same AFL script with different parameters. If I have an AFL with
significantly long runtime per optimization step (e.g. 1 minute) the
overhead for the multi-threading should become quite small and
independent tasks should scale nearly with the number of CPUs (as long
as there is sufficient memory, n threads might need n-times more
memory than a single thread). For sure the situation is different if
my single optimization run takes only a few millisecs or seconds, then
the overhead for multi-thread-managment goes up ...

Maybe Tomasz can give some detailed comments on that issue?

Best regards,
Markus

--- In amibroker@xxxxxxxxxps.com, "dloyer123" <dloyer123@x..> wrote:
>
> Running on my core 2 laptop, running two copies of AB, doing
> optimizatios will slow down both, but not by half. So, running on 1
> core, might take 1 minute per pass, two cores can run 2 passes in 1.5
> minutes.
>
> But... The two passes are independent and dont know about each other
> and are not part of the same optimization run.
>
> Also... The dual cores can be had at 3GHz, the quad cores at less.
>
> So, it is hard to keep 4 cores busy and the contention will be worse.
>
> I just ordered a new optimization system myself. I went with the 3Ghz
> Core 2 dual, with 4GB of DDR2(800) ram. There is faster ram available,
> but at a much higher cost and benchmarks dont show much benifit.
>
> --- In amibroker@xxxxxxxxxps.com, "Steve Dugas" <sjdugas@> wrote:
> >
> > Hi - OK, I decided to get a new computer for optimizations. I can get
> either a dual-core or a quad-core. I know TJ has run tests and decided
> not to rewrite AB's optimizer for multi-core, but I think I remember
> someone saying that they were getting a speed boost by running 2
> instances of AB on a dual-core machine? So, if I got a quad-core and
> ran 4 instances, would they each use a different core and give me a 4X
> speed increase? If not, could it possibly be *slower* to get a quad-
> core if all instances of AB are trying to use only one core ( 1/4 of
> computer's power, vs 1/2 for a dual-core )? Sorry for the stupid
> questions, I hope someone knows more about it than me. 8 - )
> > Thanks!
> >
> > Steve
> >
>