Channel

template<CommunicationSpace CommSpace = MpiSpace>
class Channel

An MPI persistent communication channel for repeated point-to-point exchanges.

Only the Channel<MpiSpace> specialization is currently provided.

Channel binds a fixed source rank, destination rank, and message tag. After registering send and receive buffers with sendinit() and recvinit(), the user calls start() to launch all registered operations and wait() to block until they complete.

Each registered operation is represented by a persistent MPI request. Register the communication pattern once, then repeat start / wait cycles to execute the same operations. The persistent requests are released when the channel is destroyed.

A persistent request retains the buffer address, element count, and datatype supplied during registration. Channel does not retain the View object or its allocation. The application must therefore keep every registered buffer allocation valid and at the same address until the channel is destroyed. Between a completed wait() and the next start(), send buffers may be modified and receive buffers may be read or modified. While an operation is active, the usual MPI buffer-access restrictions apply.

The communicator is borrowed rather than duplicated. It must remain valid until the channel is destroyed, and the channel must be destroyed before MPI_Finalize. Every call to start() must be matched by a successful wait() before destruction.

Template Parameters:

CommSpace – The communication backend. Only MpiSpace is supported.

explicit Channel(int dest_rank, int src_rank, int tag, MPI_Comm comm)

Constructs a Channel with fixed endpoints.

Parameters:

  • dest_rank – The destination rank for send operations.

  • src_rank – The source rank for receive operations.

  • tag – The message tag.

  • comm – The borrowed MPI communicator used by every registered operation.

~Channel()

Releases all registered persistent requests with MPI_Request_free. The channel must have no active operations; the destructor does not wait for them.

Channel(const Channel&) = delete
auto operator=(const Channel&) -> Channel& = delete

Copy construction and copy assignment are deleted because a channel exclusively owns its persistent requests.

Channel(Channel &&other) noexcept

Transfers ownership of all persistent requests and the borrowed communicator from other. The moved-from channel is empty and may be safely destroyed.

auto operator=(Channel &&other) noexcept -> Channel&

Releases the destination’s existing persistent requests, then transfers ownership from other. The moved-from channel is empty and may be safely destroyed.

The destination must have no active operations before assignment.

template<class SendView>
void sendinit(SendView view)

Registers a send buffer with the channel.

The View’s data type determines the element type communicated. Its underlying allocation must remain valid until the channel is destroyed.

Each call registers an additional persistent send operation.

Template Parameters:

SendView – A Kokkos View type.

Parameters:

view – The view to register as a send buffer.

template<class RecvView>
void recvinit(RecvView view)

Registers a receive buffer with the channel.

The View’s data type determines the element type communicated. Its underlying allocation must remain valid until the channel is destroyed.

Each call registers an additional persistent receive operation.

Template Parameters:

RecvView – A Kokkos View type.

Parameters:

view – The view to register as a receive buffer.

void start()

Activates all registered persistent requests.

All pending Kokkos kernel work is fenced before the communication operations are initiated, ensuring that send buffers are fully populated and receive buffers are not in use.

void wait()

Blocks until all active persistent requests have completed.

Upon return, the persistent MPI requests become inactive but remain registered. Call start() again to repeat the same communication operations.