[Dune] New subentity numbering

[Martin Nolte]

Hi Peter, hi Christian,

first of all, let me state that (not knowing your discussion), I did not see the 
point of Sven's mail. Having read your mail, I think I can understand what you 
mean. And now this is constructive (so no offense taken).

It is correct, that we have to work on documentation a lot before a release 
(especially the user-oriented part). We also have to state clearly why we 
changed what and I think we can at least provide some hints there. I also have 
to admit that we can no longer see many of the problems with this numbering 
stuff, since we have gone too deep into it. This is exactly where we need help. 
Ask what you don't understand and then write it in such a way that everybody can 
understand it. For us this is really hard, since we don't see the problems anymore.

I also admit, that it would have been nice to have a numbering that is nearer to 
the old one. In fact, we discussed a lot about it and didn't see how. I somehow 
has a brilliant idea, he should come forward, state it and then implement it. 
I'm the last guy to say the current implementation cannot be improved. But be 
warned: The implementation and testing easily swallows months.

As to Christian's remarks about validity of wrong code: This was exactly what we 
feared, when we suggested a smooth transition. A hard break would have meant 
that you don't even find the places. Now, you "only" have to be extra careful. 
Of course, we also have run into this problem. At least, we stand a chance to 
find the places, now.

I really understand the worries about these changes. Actually, in Heidelberg I 
had the impression, that I was one of the guys who most feared this change. It 
is really hard to communicate the problems (especially for the subentity 
relation, where there was no previous documentation). So, if anybody is unsure 
how the change will affect his code, feel free to ask us. There is no stupid 
question with respect to this.

Maybe, we all are also invited to create some documentation page with the common 
pitfalls. If someone makes a mistake, he could simply add it there.

I hope, this throws some light onto why we always said we needed help with the 
transition.


Yours,

Martin



Christian Engwer wrote:
> Hi Martin,
> 
>> In case this e-mail hurts somebodies feelings, I want to apologize in advance.
>> The destructive criticism of the previous mails is not easy to take, if you
>> respect the opinion the authors.
> 
> I can only speek for my self, but I doubt that Sven intendet his email
> to be destructice. There was ne goal to be acieved with te new
> numbering, namely to be generic. We discussed how to achieve this and
> we agreed that it must be in a way such that the user doesn't break
> his code without knowing and such that the user would have to change a
> few places as possible.
> 
> Now for the first part, we all failed misserably. That is not
> particularly cour fault, we all could have helped in improving the
> documentation, we find it lacking. But I also must state that the
> amount of work is bigger than I'd expected during the discussion.
> 
> For the second point we realized during the transition of code in
> Heidelberg, that it is easy to miss a point where the numbering
> changed and end up with valid code, but wrong results. I'm sure you
> made similar experience.
> 
> Currently we have a bad situation and I'm not sure what is the best
> solution, but still I think it is a valid to discuss this situation.
> 
> I wouldn't like to get rid of the generality again, but I also fear
> the trouble that is still lying in front of us and that that's coming
> after a release.
> 
> Lastly I'd like to say, you are right that there is no use just
> moaning. Either there is a working generic algorithm, or everything
> has to stay as it is. But this still doesn't answer the (my) question:
> "should we consider switching to yet an other numbering (before the
> release) which is consistent with the existing cube and simplex
> numbering, assuming we would find one?"
> 
> Please don't take this personal or destructive.
> 
> Christian

-- 
Martin Nolte <nolte at mathematik.uni-freiburg.de>

Universität Freiburg                                   phone: +49-761-203-5642
Abteilung für angewandte Mathematik                    fax:   +49-761-203-5632
Hermann-Herder-Straße 10
79104 Freiburg, Germany