`gko::experimental::mpi::communicator`#

Owning C++ wrapper around MPI_Comm. Every distributed Ginkgo type (distributed::Matrix, distributed::Vector, distributed::Partition consumers, …) carries one of these. The class is reference-counted, so passing it by value is cheap and the underlying MPI_Comm is freed when the last communicator instance goes out of scope.

Most application code constructs a communicator once around MPI_COMM_WORLD (or a derived communicator) and threads it through the distributed types it creates.

gko::experimental::mpi::communicator comm{MPI_COMM_WORLD};
auto mat = gko::experimental::distributed::Matrix<...>::create(exec, comm);

The rank() and size() accessors return the current rank and total process count without going through MPI_Comm_rank / MPI_Comm_size on every call.

class communicator#

A thin wrapper of MPI_Comm that supports most MPI calls.

A wrapper class that takes in the given MPI communicator. If a bare MPI_Comm is provided, the wrapper takes no ownership of the MPI_Comm. Thus the MPI_Comm must remain valid throughout the lifetime of the communicator. If the communicator was created through splitting, the wrapper takes ownership of the MPI_Comm. In this case, as the class or object goes out of scope, the underlying MPI_Comm is freed.

Note

All MPI calls that work on a buffer take in an Executor as an additional argument. This argument specifies the memory space the buffer lives in.

Public Functions

inline communicator( const MPI_Comm &comm, bool force_host_buffer = false, )#

Non-owning constructor for an existing communicator of type MPI_Comm. The MPI_Comm object will not be deleted after the communicator object has been freed and an explicit MPI_Comm_free needs to be called on the original MPI_Comm object.

Parameters:

comm – The input MPI_Comm object.
force_host_buffer – If set to true, always communicates through host memory

inline communicator(const MPI_Comm &comm, int color, int key)#

Create a communicator object from an existing MPI_Comm object using color and key.

Parameters:

comm – The input MPI_Comm object.
color – The color to split the original comm object
key – The key to split the comm object

inline communicator(const communicator &comm, int color, int key)#

Create a communicator object from an existing MPI_Comm object using color and key.

Parameters:

comm – The input communicator object.
color – The color to split the original comm object
key – The key to split the comm object

communicator(const communicator &other) = default#

Create a copy of a communicator.

Potential ownership of the underlying MPI_Comm will be shared.

inline communicator(communicator &&other)#

Move constructor.

The other communicator will relinquish any potential ownership and use MPI_COMM_NULL as underlying MPI_Comm after the move operation.

communicator &operator=(const communicator &other) = default#

gko::experimental::mpi::communicator#

`gko::experimental::mpi::communicator`#