[Users] CarpetIOHDF5::output_index = "yes" by default?

[Erik Schnetter]

If it is possible to generate the index files as post-processing step, then
I would prefer that, as it reduces the time the simulation spends waiting
for I/O. We could add it e.g. to Simfactory's cleanup step to have it
happen automatically.

How well-documented are the index files? If they are generated by default,
then there should be a section in CarpetIOHDF5's thorn guide (or in the
Visit reader's documentation) describing why they are a good idea, and what
information they contain, and how they can be used to speed up input.

-erik



On Wed, Feb 27, 2013 at 2:41 PM, Roland Haas <roland.haas at physics.gatech.edu
> wrote:

> Hello all,
>
> > Would somebody object to making CarpetIOHDF5::output_index = "yes" the
> > default? (It is currently "no".)
> >
> > It should not hurt to create these small files. (Or, does it?)
> It creates files which in itself might be bad. Creating files can be an
> issue on some file systems where creating files is slow (or there might
> be limit on the number of files, that apparently on some clusters
> [admittedly I know of no Cactus users there] can be as low as 1e6 files
> *total*).
>
> Also currently there is a bug/mis-feature in that output_index writes
> indices for both data and checkpoint files. The later probably should
> have a separate switch since index files are less useful there.
>
> If the issue is that we currently have no method for users to create
> index files for existing HDF5 files once eg they find that visualization
> is slow, then for that I have a modified version of hdf5_merge (or was
> it hdf5_extract... anyway one of them) where I simply commented out the
> final H5Dwrite and which generates perfectly fine index files (of the
> "new" format that do not have the extra attribute with just that change
> or "old" ones with the attribute with the obvious changes [that are also
> in]). It's of course a bit of a hack since the tools were not originally
> meant to do that.
>
> Yours,
> Roland
>
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-- 
Erik Schnetter <schnetter at cct.lsu.edu>
http://www.perimeterinstitute.ca/personal/eschnetter/
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