6.338 lecture 13: mpi.jl

MPI terminology

MPI: Message Passing Interface

MPI.init(): Initializes the MPI environment

MPI.COMM_WORLD: the MPI communicator- everything processes need to communicate

MPI.Comm_rank: an integer 0:N-1; each MPI process has a different rank, you can think of it as a process ID

MPI.Comm_size: the number of MPI processes (N)

Barrier: all process wait until everyone reaches this point

Send/Receive: Point-to-point communication: rank i sends a message to rank j and rank j receives a message from rank i

Blocking/Unblocking: Blocked send/receives wait until the message has been sent or received before proceeding; unblocking send/receives continue

Broadcast: one-to-all communication: rank i sends message to rank 0:i-1,i+1:N

Gather: all-to-one communication: rank 0:i-1,i+1:N sends message to rank i

Reduce: all-to-one communication: gather messages onto rank i and perform a reduce operation

Scatter: one-to-all send one piece to each

module load mpi/mpich-x86_64 module load julia-latest

julia: ]add MPI