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mpi.md

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Simple

MPI_Init(NULL, NULL);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &world);

Blocking communication

MPI_Recv(
    void *buffer, int count, MPI_Datatype, 
    int source, int tag,
    MPI_Comm comm, MPI_Status *status
)

MPI_Send(
    void *buffer, int count, MPI_Datatype,
    int destination, int tag, 
    MPI_Comm comm
)
MPI_Probe(int source,int tag, MPI_Comm, MPI_Status*) // check if message is ready
MPI_Get_count(MPI_Status *status,MPI_Datatype dtype,int *count)

MPI_ANY_TAG    // matches any tag
MPI_ANY_SOURCE // matches any source
MPI_COMM_WORLD // matches any comm

Optimized sends/receives

Ssend(...)     // synchronized
MPI_Rsend(...) // "ready"

Non-blocking communication

MPI_Isend(…,MPI_Request *request)
MPI_Irecv(…,MPI_Request *request)

MPI_Iprobe(int source,int tag,MPI_Comm,int *flag,MPI_Status
*status) // like probe but nonblocking

Waiting (blocking)

MPI_Wait(MPI_Request *,MPI_Status *)
MPI_Waitany(int count,MPI_Request *,int *index MPI_Status *status)
MPI_Waitall(int count,MPI_Request *,int *index MPI_Status *status)

Testing (non-blocking)

Check for completion

MPI_Test(MPI_Request *request,int *flag,MPI_Status *status)
MPI_Test[any|all](int count,MPI_Request *,int *index,int *flag,MPI_Status *)

Status

MPI_Status status;
status.MPI_TAG; status.MPI_SOURCE; status.MPI_ERROR;

Datatypes

MPI_Type_contiguous(int count,MPI_Datatype, MPI_Datatype *newdatatype)
MPI_Type_vector(int count,int blocklength,int
stride,MPI_datatype,MPI_Datatype *newdatatype) // separate by stride

Collective communication

MPI_Barrier(MPI_Comm)
MPI_Gather()
MPI_Scatter()

Other

MPI_Cancel(MPI_Request*)
MPI_Comm_spawn
MPI_Comm_spawn_multiple