Inverse(fes.FreeDofs()) does not do anything

Dear all,
I have a weird problem and I am not sure, if I should copy the whole problem

I use NGSolve on two PCs, the code part

hmat = a.mat.CreateMatrix()
hmat.AsVector().data = 0.5 * tau * a.mat.AsVector() + m.mat.AsVector()
inv = hmat.Inverse(fes.FreeDofs())

does not run on the PC A and on the other, PC B everything runs smoothly. Both PCs use the exact same file synched over a cloud service
I get no error or anything, it is simply stuck. Before I updated to ubuntu 20.04, this february, also PC A had no problem with the file

There should be no problem with that code.
After updating, did you update ngsolve as well?
Can you run ngsolve in a gdb session and give us a backtrace where it hangs?

Dear Christopher
I installed anaconda and afterwards reinstalled ngsolve

I have a print directly infront of it

inv = hmat.Inverse(fes.FreeDofs())

and afterwards

So it is the inverse I guess. As written, no errorcode.

I also checked it via

ngsglobals.msg_level = 0 

no feedback

therefore one question, for me it feels like ngsolve doesn’t find the solver for the inverse
can the reason be, that I start ngsolve via


And now I start googling how to run ngsolve in a gdb session, will post results

Thanks for the help!

Setting this to 0 gives no output. Set it to some high value (i.e. 7 for maximal output).

Have you tried installing ngsolve in a dedicated environment using conda?


No, I haven’t yet. When doing it on 7 (thanks) I get

call umfpack ...

Can it be that he doesn’t find umfpack because I have to set the paths manually via


before I start ngsolve