fenics team mailing list archive

[Johan Jansson <johanjan@xxxxxxxxxxxxxxxx>]

On Tue, Sep 27, 2005 at 08:41:26AM -0500, Matthew Knepley wrote:
> Johan Jansson <johanjan@xxxxxxxxxxxxxxxx> writes:
> 
>       More than 50% of Petsc downloads (we estimate) are for the
> Windows version, which we also surmise is not a supercomputer. There
> is no difference in our application code that runs on a supercomputer
> from what I run on my laptop. In fact, I do all development on the
> laptop, and only move to the supercomputer for VERY large runs (the
> overwhelming amount of supercomputer usage is robbery of the taxpayer).
> 

That sounds great, and is probably contributing to keeping PETSc
healthy.


>       The above paragraph is meant to support the thesis that there
> need not be any difference between development for a laptop and a
> supercomputer. In my view, parallelism is recognition of structure
> inherent in the problem. Witness the difference between "parallelism"
> in densse and sparse linear algebra. They bear almost no relation to
> each other. In fact, the parallelism in sparse linear algebra has the
> same root as parallelism in FEM. This point is made forcefully in the
> Sieve paper.
> 
>       Thus, I would be interested in any aspect of FENICS software that:
> 
>   1) Makes it hard for a laptop user to code/run
> 
>   2) Prevents it from running on a supercomputer
> 
> I do not see antagonism between these goals.
> 
>   Thanks,
> 
>         Matt
> 

The main point I was attacking with my post was the suggestion that we
should sacrifice performance by not pre-compiling code, since the
Linux version Blue Gene runs (and perhaps other supercomputer
operating systems) apparently can't do dynamic loading. This would
impact your laptop user, since his code would run slower. A better
solution as far as I can see would be to fix Linux on Blue Gene so
that it can do dynamic loading, or alternatively avoid dynamic loading
by recompiling and reuploading the code to the nodes between runs.

As soon as DOLFIN can do parallel assembly and mesh manipulation with
Sieve, all Fenics components should run equally well on laptops and
supercomputers.

  Johan