fenics team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Sep 26, 2005 at 10:02:46PM -0500, Robert C.Kirby wrote:

> I claim load balancing will be a big issue in parallel as it is with 
> all spatially adaptive methods.

I'm sure it will be.

> On the other hand, even the monoadpative solver could be a big 
> breakthrough for some of these codes (*arbitrary* order + global error 
> control) and would be easier to make efficient enough for prime time.

Good point. Same thing here though, dual problems and global error
estimates are temporarily broken since Johan Jansson and I rewrote the
core during the winter/spring and haven't had time to put everything
back in. I too often find myself in this situation, doing development
by regression: each new version has fewer features than the previous...

> >In general, no one cares about the size of the global error. At least
> >not when solving ODEs. People only care about the local error (which
> >is something very different).
> >
> To set a new standard, you have to say this loudly, use small words 
> (you seem to have done this well so far), and show concrete examples as 
> to why controlling only local error gets you into trouble (things like 
> collapsing bridges or exploding power plants are especially helpful at 
> convincing engineers; theorems are not).  In the absence of 
> catastrophe, people might consider staggering performance results on 
> particular problems they care about.  These problems obviously are very 
> special cases and have nothing to do with problems you or anybody else 
> cares about.

Good point, and I will push it when I can back up my claims with code.

/Anders