[Dune] A question on CollectiveCommunication

[Aleksejs Fomins]

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Dear Dune,

I am trying to understand the paradigm of the communication used in Dune

The question concerns the following
Dune::CommDataHandleIF< DataHandleImp, DataTypeImp >

and

int Dune::CollectiveCommunication< C >::gather( T * in, T * out, int
len, int root) const

In both cases we define a template parameter which defines the data
type to be communicated. As I understood from discussions with Marcus
and Peter, internally the communication is performed using MPI_BYTE
communication, i.e. sending size_of(T) data from a given address to a
given address.

It looks to me that this should not work for T = some stl object, because:
1) If T has variable size, and we are passing a pointer to the array
of T's in gather, then gather has no information on the length of each
individual T
2) If I would like to communicate T = std::vector<int>, would not the
internal implementation of vector contain a pointer to an array for
the current processor?

That said, the question is as follows:

Is dune communication interface intended to handle standard stl types?
If no, which DataTypes are expected/allowed to be communicated?

Regards,
Aleksejs
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