ERROR: 'energy_groups' attribute must exist!

User Support
1

Hello,
Please see in the first file attached the given error when I run openmc code in multigroup mode, and the second file is the simulation in continuous mode of energy, I configured it successfully in my machine ubuntu and it seems to work very well.
Why in multigroup mode this error show up?

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image2.png
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2

Hi Mohamed,

In order to run in multi-group mode, you will need to have a multi-group cross section HDF5 library. My guess is that you are trying to run in multi-group mode but are using continuous-energy cross sections.

Best,
Paul

3

Thanks for the reply
I tried to run an example “pincell multigroup” provided with the code. By following these steps. Here’s what I got I think that my own library section HDF5 multi-group -mgxs.h5- was well generated but I do not know how to set the OPENMC_MG_CROSS_SECTIONS environment variable to the absolute path

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4

Hi Mohamed,

That’s interesting. You shouldn’t need to set OPENMC_MG_CROSS_SECTIONS for this problem as the materials.xml file (or settings.xml depending on the exact point in time of the code base you’re using) should contain a cross_sections attribute which states that the file is the mgxs.h5 file in your directory. Can you confirm that line is there?

5

Hi Adam
Here is the contents of the materials.xml file

<?xml version='1.0' encoding='utf-8'?>

<cross_sections>./mgxs.h5</cross_sections>








6

Interesting. Let’s see if the mgxs.h5 file at least has that data in it or if it somehow was corrupted during the course of build_xml.py. Can you run the following command in the examples/python/pincell_multigroup problem and include the output here:

h5dump -a energy_groups ./mgxs.h5

Also, does the examples/xml/pincell_multigroup problem run successfully?

Thanks,
Adam

7

Hi Adam
the output of command : h5dump -a energy_groups ./mgxs.h5 shows that the attribute energy_groups is absent

HDF5 “./mgxs.h5” {
ATTRIBUTE “energy_groups” {h5dump error: unable to open attribute “energy_groups”

}
}

8

Thanks Mohamed. Sounds like a malformed library, which is odd considering you had no error messages. Would you mind attaching the mgxs.h5 file to this message?

mgxs.h5 (16.3 KB)

9

Sorry I didn’t realize I had the attachment to my message still - that is an mgxs file that my machine created but it is for a version that wont be compatible with the one you are using so disregard it.