Examples:

• MPI_Send

call MPI_Send(x,m,MPI_REAL8,...)

Probe mpi_send_start reports that 8*m bytes are to be sent.

• MPI_Recv

call MPI_Recv(x,n,MPI_REAL8,...)

Probe mpi_recv_end reports the number of bytes that were actually received, which must be at most 8*n.

• MPI_Sendrecv

call MPI_Sendrecv(x,m,MPI_REAL8,...,y,n,MPI_REAL8,...)

Probe mpi_sendrecv_start reports that 8*m bytes are to be sent, and probe mpi_sendrecv_end reports the number of bytes that were actually received, which must be at most 8*n.

• MPI_Irecv, MPI_Wait

integer req
call MPI_Irecv(x,n,MPI_REAL8,...,req,...)
call MPI_Wait(req,...) 

Probe mpi_wait_end reports the number of bytes that were actually received, which must be at most 8*n.

• MPI_Isend, MPI_Irecv, MPI_Wait

integer reqs(2)
call MPI_Isend(x,m,MPI_REAL8,...,reqs(1),...)
call MPI_Irecv(Y,N,MPI_REAL8,...,reqs(2),...)
call MPI_Waitany(2,reqs,...)
call MPI_Waitany(2,reqs,...) 

Probe mpi_isend_start reports that 8*m bytes are to be sent. The MPI_Waitany call that completes the receive will show the number of bytes that were actually received, which must be at most 8*n, in its mpi_waitany_end probe. The other MPI_Waitany call, which completes the send, will report 0 bytes received.

• MPI_Waitall

integer reqs(8)
call MPI_Isend(x1,m,MPI_REAL8,...,reqs(1),...)
call MPI_Isend(x2,m,MPI_REAL8,...,reqs(2),...)
call MPI_Isend(x3,m,MPI_REAL8,...,reqs(3),...)
call MPI_Isend(x4,m,MPI_REAL8,...,reqs(4),...)
call MPI_Irecv(x5,n,MPI_REAL8,...,reqs(5),...)
call MPI_Irecv(x6,n,MPI_REAL8,...,reqs(6),...)
call MPI_Irecv(x7,n,MPI_REAL8,...,reqs(7),...)
call MPI_Irecv(x8,n,MPI_REAL8,...,reqs(8),...)
call MPI_Waitall(8,reqs,..) 

Probe mpi_isend_start reports that 8*m bytes are to be sent in each of the four MPI_Isend cases. Probe mpi_waitall_end reports the number of bytes that were actually received, which must be at most 4*8*n.