On Jul 2, 3:49 pm, Bill Hart <goodwillh...@googlemail.com> wrote:
> Support for parallel processing can make demands on people's compiler,
> because ultimately there is no point writing parallel code for very
> old machines and newer machines will have newer compilers. If you are
> really serious about performance and using multi core machines, you
> are probably going to own a modern machine with the latest compiler.
> Of course it will always be possible to build MPIR in single core
> mode, which will be the default, so it is not like we are making a
> recent gcc a prerequisite to build MPIR.
>
> In particular gcc 4.2.4 and following have OpenMP support built in.
> That means all the compilers which are derivatives of gcc will fairly
> shortly have OpenMP support if they don't already. Certainly the Intel
> compiler supports OpenMP and has for quite some time.
>
> As you say, the main issue is MSVC, which doesn't even have pthreads.
> Perhaps Brian knows whether VS 2010 will have OpenMP support?
>
> Bill.
>
> 2009/7/2 Jeff Gilchrist <jeff.gilchr...@gmail.com>:
>
>
>
> > On Thu, Jul 2, 2009 at 10:22 AM, Bill Hart<goodwillh...@googlemail.com>
> > wrote:
>
> >> That is an interesting question. pthreads is certainly available on
> >> much older compilers. But the issue is, it is very hard to code.
>
> > I guess it is the only thing I know, so maybe I should move to OpenMP. ;-)
>
> >> I'd be interested in supporting pthreads if there was some performance
> >> benefit from doing so, but I actually think OpenMP is pretty good.
>
> >> I recall when parallelising using pthreads problems with about 500x500
> >> = 250000 bits of data, or perhaps a little less, could be effectively
> >> parallelised. We are currently parallelising stuff effectively with
> >> 128000 bits of data.
>
> >> In other words, there doesn't seem to be any immediately obvious
> >> performance reason to consider pthreads.
>
> > From a performance perspective, I have no idea. I was thinking more
> > from a support perspective. Pthreads is available on every system
> > under the sun (except MSVC natively). I haven't looked lately but do
> > any compilers come with OpenMP support built-in? I'm not sure how
> > easy it will be to get OpenMP working in MSVC (which doesn't really
> > support pthreads either so might have to make a Windows threads
> > version anyways). If OpenMP is widely supported now then it would
> > probably make more sense just to support one, the one that is easier.
>
> > Jeff.
MSVC has had OpenMP support for some time now.
Visual Studio 2008 supports OpenMP 2.0; Visual Studio 2010 supports
OpenMP 3.0
I have used pthreads on MSVC in the past but given the native support
for OpenMP, I dropped support for pthreads about two years ago.
Brian
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