[Users] Grid structure

[Matthew Turk]

Hi Erik,

Thanks for writing.

On Fri, Feb 8, 2013 at 8:42 AM, Erik Schnetter <schnetter at cct.lsu.edu> wrote:
> Matt
>
> (You are presumably speaking of the grid structure stored in HDF5 output
> files, including in checkpoint files.) What do you intend to do with the
> grid structure you so obtain?

Yup, that's the structure I'm referring to.  I hope to reconstruct the
mesh in memory; I have some data I'd like to examine in yt (
 http://yt-project.org/ ) which requires understanding the spatial
layout of all the grid patches.  Right now I'm able to load the data
in, make plots, etc, but I'm stuck at a few of the details, and I was
hoping to either track it down inside the parsing by perhaps using a
second approach to the problem.

>
> If you are interested in the exact grid structure, then yes, this is the
> correct way to do so. For example, when Carpet reads a grid structure e.g.
> for recovery, it uses this information.
>
> However, if you e.g. want to visualise data, then there is an alternative.
> Each dataset (HDF5 component) contains attributes describing the coordinate
> of its upper left corner as well as the coordinate distance between grid
> points (grid spacing). This should suffice to correctly combine the datasets
> you read in, and may be much simpler than parsing the grid structure.

Ah, this will be very helpful!  I'll attempt to use this information instead.

>
> Note that the VisIt visualisation toolkit knows how to read Carpet output.
> You could look at its reader for details.
>
> If you are really interested in parsing the grid structure, then it may be
> easier to discuss this in person. Are you available on Monday morning 11:00
> EST for the Einstein Toolkit telecon? I can explain things there.
>

I'd love to join in -- thank you for mentioning it!

-Matt

> -erik
>
>
>
> On Fri, Feb 8, 2013 at 8:15 AM, Matthew Turk <matthewturk at gmail.com> wrote:
>>
>> Hi all,
>>
>> I was wondering if someone could point me at how to parse the grid
>> structure information in a Cactus output.  I hope this is the right
>> venue for this type of question.
>>
>> In the output I'm examining, under the "Parameters and Global
>> Attributes" node at root level, there's a "Grid Structure v5" dataset,
>> which contains "grid_superstructure" and "grid_structure".  Is parsing
>> the string affiliated with the grid_superstructure component the best
>> way of identifying the spatial extent, dimensions and refinement level
>> of grids in the output?
>>
>> Thanks very much for any pointers,
>>
>> Matt
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>> Users at einsteintoolkit.org
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>
>
>
>
> --
> Erik Schnetter <schnetter at cct.lsu.edu>
> http://www.perimeterinstitute.ca/personal/eschnetter/