Hi Anthony, I can replicate this problem, as can Sam. Here's what I think is going on. When you run in parallel and access a derived quantity, it really wants to try to batch the IO as best it can. To do this, it uses a FieldDector. This is a fake object that accepts requests for fields, data, parameters, etc. It does this by tracking accesses to fields and parameters, but it doesn't mock up a complete parameter file. The baryon overdensity field uses a non-standard method of accessing data from the parameter file, which the fake parameter file didn't know. Rather than access the dictionary directly (pf['omega_baryon_now']) it accessed it by peeking into the underlying data structure 'parameters.' I have changed this and pushed a fix to the main repository, in changeset 7270e9e83be7. If you're running from an installation you maintain, you should be able to do "yt instinfo -u" to get the latest version. Let me know if that doesn't fix it for you -- it does for me, but there might be an additional complicating factor I'm missing. -Matt On Mon, May 23, 2011 at 5:49 PM, Anthony Harness <anthony.harness@colorado.edu> wrote:

I am running yt-2.1stable with python2.7 on Kraken and run into this problem:

When I call a derived quantity that calls a derived field that calls a universal field, I get an error: "AttributeError: 'fake_parameter_file' object has no attribute 'parameters'" which arises in the universal field's convert function in 'data_objects/universal_fields.py'

With the following code: #derived Field def _test2(field,data):         return data['Baryon_Overdensity']

add_field('test2',function=_test2,units=r"")

#derived quantity def _test(data):         return data['test2']

def _combTest(data,arr):         return arr.sum()

add_quantity('test',function=_test,combine_function=_combTest,n_ret=1)

dd.quantities['test']()

I get the error:

AttributeError: 'fake_parameter_file' object has no attribute 'parameters'

from line 418, in _Convert_Baryon_Overdensity in universal_fields.py: "data.pf.parameters.has_key('omega_baryon_now'):"

So it seems as if the parameter file is not being passed from the derived quantitty all the way to the universal field. This works fine when I run it in serial, but fails when it is ran in parallel. Any suggestions?

Thanks

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