CODEWITHSUNDEEP
c++mpibroadcast
sygi
sygi

Reputation: 4647

two MPI broadcasts one after another

I would like to send two arrays: double A and int B using broadcast in MPI (I'm using C++). Normally, the communicator.Bcast blocks for readers, but not for the writer. So, if I did:

communicator.Bcast(A, a_len, ...)
communicator.Bcast(B, b_len, ...)

It could happen that some process would first retrieve the second message and things would mess up.

I wonder, what is the good, clean solution for that problem? Should I use derived datatypes/MPI_Pack? It seems ugly. Can I somehow force usage of TAGs in broadcast?

Upvotes: 1

Views: 83

Answers (1)

dabo42
dabo42

Reputation: 486

MPI guarantees that collective calls on a communicator are processed in the order they are issued. So no, the readers will not retrieve the second message first - that example is save.

FYI, the MPI C++ interface has been deprecated - it's better to use the C API directly for new code.

Upvotes: 5

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