[petsc-users] DMPlexCreateGmsh

[Matthew Knepley]

On Sun, Jan 12, 2014 at 7:37 PM, Gorman, Gerard J
<g.gorman at imperial.ac.uk>wrote:

>  Hi Matt
>
>  First - really sorry for having inflicted this on you. I agree that
> there are many problems with the format and it’s not like the world needs a
> new file format. I only happened to use it for a case where there was an
> existing toolchain…which I’m now rewriting anyhow.
>
>  What is your current least detested file format for FEM that plays
> nicely with DMPlex? Exodus II?
>

ExodusII we can read, and it maintains all the markers correctly, etc. It
is currently my favorite.


> Dharmendar - you might just want to write a simple translation script if
> you are locked into gmsh for some reason. It is also a pain that the format
> does not work with paraview and other common tools out of the box.
>

If you need Gmsh, I will get it working, it just may take a little while to
sort out. You can send me small samples to test with.

  Thanks,

      Matt


> Cheers
> Gerard
>
>
>  On 11 Jan 2014, at 01:14, Matthew Knepley <knepley at gmail.com> wrote:
>
>   On Fri, Jan 10, 2014 at 3:44 PM, Dharmendar Reddy <
> dharmareddy84 at gmail.com> wrote:
>
>> Hello,
>>         I have a question and feature request regarding DMPlexCreateGmsh.
>>
>> Gmsh, mesh format outputs, physical regions in the mesh as
>> For example in the a particular 2 d mesh with eight physical regions
>> it may look like the one below
>> $PhysicalNames
>> 8
>> 1 1 "RegionName1"
>> 1 2 "RegionName2"
>> 1 3 "RegionName3"
>> 2 4 "RegionName4"
>> 2 5 "RegionName5"
>> 2 6 "RegionName6"
>> 2 7 "RegionName7"
>> 2 8 "RegionName8"
>> $EndPhysicalNames
>>
>> It would be nice to have the DMPLexCreateGmsh process this information.
>>
>> The first number in each row of name is the topological dimension (tdim),
>>
>> If the code can group all the regions with dimension < mesh dimension
>> (meshDim) as "Boundary"  and all regions with dimension =
>> meshDimension as "Region"
>>
>> Gmsh outputs (if requested) the lower dimension cells in regions with
>> tdim  < meshDim. If interpolate mesh is enabled, i would like to have
>> cells of boundary region, which in the above example will be lines and
>> points, included in the boundary strata with global numbering for the
>> facets.
>>
>
>  I really hate GMsh right now. The format is a complete cluster of
> idiocy. They allow
> outputting facets as separate lower-dimensional cells, unconnected to the
> original
> cell, so we would have to initiate a search for every insertion. Not to
> mention that sizes
> are not declared up front so that we have to run through the file in
> multiple passes. I
> really really hate these guys. Is there an overwhelming reason to waste my
> time messing
> around with a format designed by the mentally infirm?
>
>  I am willing to listen to reason, but reading Gmsh files would make
> anyone unreasonably angry.
>
>      Matt
>
>
>> This ways the total number of Cells in the mesh will be : NumNodes +
>> NumLines+ NumTriangles or NumNodes+ NumTriangles (if interpolate is
>> off)
>>
>>
>> In the Current implementation, correct me if i am wrong, I see the the
>> total number of cells = numNodes + (some Lines which are elements of
>> the lower dimensional regions) + numTriangles
>>
>>
>> Thanks
>> Reddy
>>
>>
>> --
>>
>
>
>
>  --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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