CODEWITHSUNDEEP
c++mpi
Thermodynamix
Thermodynamix

Reputation: 367

Using MPI_Scatter with C++ - Scattering over different communicators

In C++, an example for using MPI_Scatter is:

MPI::COMM_WORLD.Scatter(sendbuf, 100, MPI::INT, recvarr, 100,MPI::INT, root);

This scatters the contents of sendbuff into 100 separate process to make recvarr on each process, but ONLY in the MPI World communicator.

Unlike MPI_Scatter in C, the C++ version doesn't have an input for the communicator. How can I modify this example to work for any communicator, and not just MPI_COMM_WORLD?

For example, say my communicator is named comm. How can I scatter sendbuff within the comm communicator group instead of MPI_COMM_WORLD?

Upvotes: 1

Views: 330

Answers (1)

Phil Miller
Phil Miller

Reputation: 38118

comm.Scatter(sendbuf, 100, MPI::INT, recvarr, 100,MPI::INT, root);

The object to the left of the . is the MPI communicator argument. MPI::COMM_WORLD happens to be a pre-defined instance of an MPI communicator that corresponds to the C binding's pre-defined MPI_COMM_WORLD

Note that the MPI C++ bindings have been deleted in MPI-3.0, because they were underused, hard to maintain, and had clunky misunderstandings like this.

Upvotes: 5

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