Re: Dolfin mesh conversion functions [was: Re: Welcome GSoC students!]

[c.]

Hi Marco, 


On 8 Jun 2013, at 09:01, Marco Vassallo <address@hidden> wrote:

> I've seen that a lot of time it could be interesting a refinement around one 
> of the
> boundaries (e.g. for the boundary layer problem) and so I was thinking about 
> something like
> 
> mesh_refined = msh2m_refined(mesh, boundary = 3)
> 
> but as you said below maybe now it is better to move to more general problems.

Now I see what you mean, indeed also gmsh has a nice feature which allows to 
refine
near a given geometrical entity (a face or edge of the boundary or a subdomain 
region)
and it would be cool to be able to do the same here.

But this is not crucial at this particular time, so, for now, just add a TODO 
comment in the 
function for later.

> I'm doing something like
> msh2m_oct_to_xml
> msh2m_xml_to_oct

there are many xml-based formats for storing meshes, for example:

http://www.vtk.org/Wiki/VTK_XML_Formats
http://www.ogre3d.org/tikiwiki/tiki-index.php?page=Ogre+meshxml+DTD

using "xml" in the function name is not descriptive and is misleading.

> and the same for 3D.. I don't want to put some specific reference to dolfin
> because xml is more general.

xml is indeed more general, but your functions can deal only with a very 
specific type of xml
files which are those produced by or for dolfin to represent FE meshes, and 
this should be made 
clear in the function name and in its documentation.

so, if there is no reason to separate 2d and 3d functions I'd rather use 
something like

mshm_dolfin_read
mshm_dolfin_write

if the functions must be implemented separately then

msh2m_dolfin_read
msh3m_dolfin_read
msh2m_dolfin_write
msh3m_dolfin_write

could be a good option

> ok..so maybe it could be useful to add comments also inside the code and
> not only the general explanation on top of it??


the approach I (and some other developers, but not all) like is rather to limit
comments within the code to cases where you are doing something obscure and/or 
very non-standard.

Otherwise well written and formatted code should be self explanatory, here is 
an example
I often like to show which is taken by a (real but anonymous) student's exam 
project.

the code below has a very verbose comment, but still this doesn't make it any 
clearer:

   # initialize the value of the variable nds
   # here we choose the value 1
   nds = 1;

this line of code is not commented but it is easy to understand what is going 
on:

   number_of_space_dimensions = 1;

That said, my own code may use a lot of improvement in terms of readibility ;)

> : prepare a makefile so that your functions can be built automatically when 
> doing "pkg install msh"

you could add a configure script to the source directory, if there is one pkg 
will automatically run it.

Hope this helps,
c.