[Users] Enhancements to Multipole

Ian Hinder ian.hinder at aei.mpg.de
Fri Dec 10 04:42:42 CST 2010

On 9 Dec 2010, at 17:46, Frank Loeffler wrote:

> On Thu, Dec 09, 2010 at 04:43:53PM +0100, Ian Hinder wrote:
>>> Do you think that most people would actually use the hdf5 version?
>> I expect that people have very high inertia.  However, on production filesystems, having a large number of output files is frowned upon, and makes things quite slow, so I would encourage people to use HDF5 output whenever possible.
> That is why I asked. I would expect most people to use the hdf5 version
> now.
>> I think this would be surprising to some people.  Imagine that you were happily using ASCII output in Multipole, and one day decided to include the HDF5 thorn in your thornlist because of something completely unrelated.  The next time you ran, you would find that there was no ASCII output for Multipole, and all your analysis scripts would not be able to deal with the HDF5 data.  I would adhere to the principle of least surprise.
> I agree that this could happen. What about if the thorn would provide a
> utility (script) which uses h5dump to create the ascii-output from the
> hdf5 one?

This is a good idea in any case.  But I don't think that activating or deactivating a thorn should change the output behaviour of another thorn - it is too unexpected.

>> If we want to encourage people to use HDF5 output, we could enable HDF5 by default, but I would not like to disable ASCII by default just yet.  I don't want to enable HDF5 by default just yet, as I don't know what the performance impact of it will be.  Especially on clusters with slow filesystems (I'm looking at you, Kraken).  We could enable it by default after it has seen some more testing.
> Yes, we could do that. However, production runs wouldn't all see the new
> version right now anyway (most of them will probably use the released
> version, right).

Do people use the released version for production runs?  I don't.  But then, I also don't routinely update my main Cactus tree.  There is little enough development going on in critical areas that this doesn't seem important.  

Ian Hinder
ian.hinder at aei.mpg.de

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