ncclSend Interface

interface

Send data from sendbuff to rank peer.

Rank peer needs to call ncclRecv with the same datatype and the same count as this rank.

This operation is blocking for the GPU. If multiple ncclSend() and ncclRecv() operations need to progress concurrently to complete, they must be fused within a ncclGroupStart()/ ncclGroupEnd() section.


Called by

interface~~ncclsend~~CalledByGraph interface~ncclsend ncclSend proc~execute_nccl backend_nccl%execute_nccl proc~execute_nccl->interface~ncclsend

public function ncclSend(sendbuff, count, datatype, peer, comm, stream) result(ncclResult_t) bind(c, name='ncclSend')

Arguments

Type IntentOptional Attributes Name
real(kind=c_float) :: sendbuff

Buffer to send data from
integer(kind=c_size_t), value :: count

Number of elements to send
type(ncclDataType), value :: datatype

Datatype to send
integer(kind=c_int), value :: peer

Target GPU
type(ncclComm), value :: comm

Communicator
type(dtfft_stream_t), value :: stream

CUDA Stream

Return Value integer(kind=c_int32_t)

Completion status