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Re: Enabling OpenMP by default
From: |
Thomas Weber |
Subject: |
Re: Enabling OpenMP by default |
Date: |
Mon, 18 Mar 2013 08:30:51 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Mar 12, 2013 at 11:23:06AM +0200, Susi Lehtola wrote:
> On Mon, 11 Mar 2013 21:03:30 -0300
> Júlio Hoffimann <address@hidden> wrote:
> > > I could not disagree more with this statement. It assumes no other
> > > processes
> > > ever need to use your hardware concurrently, which is usually _NOT_
> > > the case.
> > >
> > Hi Carlo, that's a good point. I always prefer write code for multiple
> > cores though, no matter the speed up. I hope as the technology
> > evolves, the performance gains will become noticeable. And of course,
> > another justification is that it can sometimes be achieved with tiny
> > effort.
>
> But this is really unintelligent behavior. Plugging in parallellism
> always includes an overhead, and because of that parallellized code can
> be *SLOWER* than the serial code.
Not necessarily. OpenMP can be used to trivially parallize for-loops,
for example. If you have a multi-core CPU (and I would be very surprised
to see someone working with Octave to not have at least a dual-core
CPU), then your operating system might already decide to switch your
process from one core to the next when it sees fit, including at every
step of the for-loop - which is the point where OpenMP parallelizes.
Having worked with OpenMP over the last 2 years, I would say that today
the sane behaviour is to *always* activate it. Operating systems have
become far better at dealing with multiple cores and the 'more than 1
core' environment is the norm today.
> Using parallellism for parallellism's sake is not sane behavior. In
> places where the operations are CPU bound using parallellism can be
> fruitful.
How much do you use Octave in an I/O bound environment?
Thomas
- Re: Enabling OpenMP by default, (continued)
- Re: Enabling OpenMP by default, Susi Lehtola, 2013/03/10
- Re: Enabling OpenMP by default, c., 2013/03/11
- Re: Enabling OpenMP by default, Júlio Hoffimann, 2013/03/11
- Re: Enabling OpenMP by default, Susi Lehtola, 2013/03/12
- Re: Enabling OpenMP by default, Júlio Hoffimann, 2013/03/12
- Re: Enabling OpenMP by default,
Thomas Weber <=
- Re: Enabling OpenMP by default, Júlio Hoffimann, 2013/03/19
- Re: Enabling OpenMP by default, Jordi Gutiérrez Hermoso, 2013/03/20
- Re: Enabling OpenMP by default, Júlio Hoffimann, 2013/03/20
Re: Enabling OpenMP by default, Thomas Weber, 2013/03/18