> you are demanding too much memory here. With your triangulation and this
> FESystem you create more than 12 million degrees of freedom. Especially with
> the Nédélec elements, which couple quite heavily, this requires a bit more
> than 64 GB of memory.

That is not quite correct. You roughly have 2 million cells that takes about
700mb in the Triangulation and you have 12.8 million DoFs: the
DoFHandler uses around 300mb for that.

The problem lies in the way you create your SparsityPattern.
dof_handler.max_couplings_between_dofs() is a very pessimistic value
as an estimate for the number of entries per row, especially in 3d. In
your case it is 1764. With this you create a SparsityPattern with 12.8
million*1764= 22 billion entries (which is too much memory!).
The first step would be replace the SparsityPattern by a
CompressedSimpleSparsityPattern and check if that reduces the number
of entries enough (see step-3).

-- 
Timo Heister
http://www.math.tamu.edu/~heister/
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