What is SYSTEM(216)?

I recently started using Patran/Nastran 2018. I just noticed that my nastran input files now have the following command at the top: NASTRAN SYSTEM(216)=YES. I do not recall seeing that with previous patran/nastran versions. Unfortunately, I cannot find this particular system cell documented in the QRG or any other manual.

Please tell me why there is no mention of system cell 216 in the QRG or any other version 2018 manual. I would like to know what this command is doing and if it is necessary. I expect all commands to be documented in your manual. Am I expecting too much?

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0 toby.t.norris over 6 years ago

Thanks for that information Don. I normally use the SMETHOD=ELEMENT to turn on the iterative solver. I was not aware of the system(216) method since it is apparently undocumented. I do not have any direct text in Patran and it is just a standard analysis output from Patran. I have lots of subcases defined and there is a good chance that I did select the iterative solver for one or more of those cases from within patran awhile back. But then I found that the iterative solver was nearly 10 times slower for my huge tet model. So I went back to the sparse solver. I was selecting the solver by manually editing the bdf file and not from with Patran. I will double check my patran db to make sure that the iterative solver option is unchecked because I do not want to use the iterative solver.

While we are on the subject of the iterative solver, I wonder if you can point me to the documentation where the difference between the ELEMENT and MATRIX methods are clearly explained. There must be two methods for a reason, and I would like to know when one method should be chosen over the other. Thanks,
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0 toby.t.norris over 6 years ago

Thanks for that information Don. I normally use the SMETHOD=ELEMENT to turn on the iterative solver. I was not aware of the system(216) method since it is apparently undocumented. I do not have any direct text in Patran and it is just a standard analysis output from Patran. I have lots of subcases defined and there is a good chance that I did select the iterative solver for one or more of those cases from within patran awhile back. But then I found that the iterative solver was nearly 10 times slower for my huge tet model. So I went back to the sparse solver. I was selecting the solver by manually editing the bdf file and not from with Patran. I will double check my patran db to make sure that the iterative solver option is unchecked because I do not want to use the iterative solver.

While we are on the subject of the iterative solver, I wonder if you can point me to the documentation where the difference between the ELEMENT and MATRIX methods are clearly explained. There must be two methods for a reason, and I would like to know when one method should be chosen over the other. Thanks,
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