Problem with Test and Trial functions used to project from gfuir -> gfu

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1

Hello,

I am currently working on a process that takes values from a numpy array and projects them back to a gridfunction. I am doing this using IntegrationRuleSpace, as explained here: GridFunction to numpy array to new GridFunction - Kunena.

The process works well, except for a weird thing that is happening during the L2 projection step (gfuir → gfu).
I am working with a mixed finite element space, so I do p and u separately. If I try to get the test and trial functions like this:

fes_p = L2(mesh=mesh, order=interp_ord-1)
fes_u = HDiv(mesh=mesh, order=interp_ord)
fes = FESpace([fes_u, fes_p])
u, p = fes.TrialFunction()
v, q = fes.TestFunction()

Do l2 projection…

I get a bunch of nans in my gfu.

However, when I get the test and trial functions like this:

fes_p = L2(mesh=mesh, order=interp_ord-1)
p, q = fes_p.TnT()

Do l2 projection…

It works well, and I have the expected values in gfu.

Why would this happen? It is my understanding that both of the methods should give the same test and trial functions.

Best,
Sajeda

2

Hi Sajeda,
can you send the complete example, otherwise it’s difficult to guess,
Joachim

3

I have attached some sample code. I have printed out the two scenarios, so the problem should be clear once you run the file.

Obviously, I have just assigned random data to gfuir, so the values are not meaningful, but you can see the main issue with the nans (coming from mixed FES trial/test functions only).

Please note that I have tested this on real data, and I have gotten the expected output for the changed gfu, so there is nothing wrong with my process.

Note: I tried to attach this as a file but it did not work, and gave me unrelated error, I tried to copy and paste the code but it did not transfer the line breaks, is there an email I can send the file to? There seem so be a lot of issues with the forum lately.

Thank you,
Sajeda