PersistentContainer has different interface depending on DUNE 2.2 or 2.3 used

[rolk]

The class PersistentContainer has a different number of template parameters depending on whether it is linked to DUNE 2.2 or DUNE 2.3, and I (who are not really familiar enough with DUNE) don't quite see the use-case for this.

Why cannot the latter parameter in the inheritance of PersistentContainerVector have an allocator? (And why cannot PersistentContainer have std::allocator as default for its third parameter?)

[rolk]

And why does dune/grid/CpGrid.hpp #include PersistentContainer at the very end; there doesn't seem to be any need for it?

[andlaus]

It seems like the PersistentContainer class is not considered an official interface by the dune guys:

http://lists.dune-project.org/pipermail/dune/2013-February/012208.html

why it is in dune-cornerpoint I cannot say, as this seems to be only needed for adaptive grids. I've opened a PR to remove it, but maybe @atgeirr or @bska can enlighten us a bit more.

[bska]

why it [the PersistentContainer] is in dune-cornerpoint I cannot say

The PersistentContainer for class CpGrid originated as contributed code (commit 0037c5d) to enable using CpGrid with the third-party (meta-grid) manager "dune-parallelgrid". Whether or not the class is actually needed or if we should continue to carry or support that interface is a question of policy. I will note, though, that according to Robert Klöfkorn (author of dune-parallelgrid), the CpGrid was (at the time of submission) among the most efficient grids available for use with dune-parallelgrid.

@atgeirr: Do you recall any additional details?

[rolk]

OK, I see; they changed the interface (between 2.2 and 2.3) in an incompatible way (removed the Allocator parameter), and we're trying to follow suite.

[andlaus]

Alright. Its better to keep this class, then?

[andlaus]

(in this case, can somebody with access to 'parallelgrid' verify that it still works? I don't have access to that project...)

[atgeirr]

I think it may be better to keep the class, and I am pretty sure updating it would be the good. However, have we solved the "how to interface with different dune versions" problem?

About the current state of dune-parallelgrid I am not quite sure, it's been some time since last I experimented with it.

[rolk]

However, have we solved the "how to interface with different dune versions" problem?

Yes, to a large extent I think we have, but of course if you mix versions of DUNE, havoc will probably ensue.