AW: [Libmesh-devel] Re: good news: 1e6 :-)

[Steffen P. <ste...@tu...>]

 
> [I posted this to the devel-list so we would have it in the archives]
> 
> How are these machines connected?  Is it 100 Mbit ethernet, or
> something faster?
> 
> A 480 Mb mesh is pretty big by my standards.  It would be interesting
> to see how long it takes meshtool to simply _read_ that mesh, and see 
> how that compares to the time it took to read the mesh in that 
> parallel simulation.  My guess is that all 15 processors were slamming

> a fileserver at the same time, requiring 15*480 = 7.2 Gb of data to be

> transfered.
> 
> Really, this poor performance is due to a lack of imagination on my 
> part.  I was thinking of something like 50Mb as a big mesh.   I will 
> re-work the read() method so that processor 0 is the only one that
> opens and reads the file.  It will then broadcast the data to all the 
> other processors.  This should be _much_ faster than the current 
> implementation.  If you could, though, see how long it takes meshtool 
> to simply read the mesh.
> 
> Another option would be to remove all the non-local elements on each
> processor.  This could be a viable option for reducing memory overhead

> when AMR is not required.  Once the mesh is parallelized it won't be 
> such an issue.
> 
> ...which brings me to your question: What are the future plans?
> 
> 1.) Obviously, parallelizing the mesh is the biggest thing to allow
> scalability to _many_ (i.e. hundreds) of processors.  This will 
> require a fair amount of work, and I'm putting it off for now.
> 
> 2.) Other than that, I think many major features are already
> implemented.  There are some small improvements that can be made, like

> moving new points to a user-supplied geometry during AMR, robust 
> smoothers, more shape functions, etc...  A lot of good stuff is in 
> there now.  Maybe some of it could be optimized.
> 
> 3.) Increase user base.  I think that the library is pretty stable
> now. More users will help make it better and they will request more 
> features.  We should improve the web page to include links to 
> presentations & stuff that use the library.  You know, "eye candy."
> Stuff to get people excited by saying "yeah, this _can_ be 
> used for big 
> stuff."


I like the documentation, but I think the main page could take a little
upgrading. Some pictures
and presentations sounds good and perhaps we could add some brief
documetations on the available
examples and applications, too.


> 4.) Whatever others want (within reason) :-)

Some things I would like to add in the near future (Daniel has already
mentioned).

Currently we are working on the Bernstein polynomials (not only
Bernstein, we'll also do
some other things, but so far Berstein seems most promising).

When we're done with the new shapes (hopefully in a few weeks), I would
like to add the slepc interface.
If that is fine by you, I would then introduce something like an
EigenSolver class and derive the slepc
interface from that class. I would probably shift some things from
SystemBase to SteadySystem, not to have
unnecessary stuff in the EigenSystem.
I'm sure the eigensolver is quite interesting for some (new) users.

Once the slepc interface is implemented, other eigensolvers (focusing on
effective solution of
quadratic eigen problems) could possibly follow (e.g. stuff Daniel has
mentioned). Again, I'm sure
this will be interesting for quite some users.

There are several more things I would like to do, e.g. some improvements
and extensions
regarding the ifems and perhaps some sort of optimization algorithm (at
this, Tetgen or any other mesh generator
could be used for shape optimization problems), but I'm not quite sure
when I'll find time to do that. 

Steffen