// Initializes MPI. Needed to use other functions.
MPI_Init( // out int Error value
&argc, // i/o int* Number of program arguments
&argv // i/o char*** Program arguments
);
// Tears down MPI. Cannot call MPI funcs after this.
MPI_Finalize(); // out int Error value// Gets the ID of the current processor.
MPI_Comm_rank ( // out int Error value
MPI_COMM_WORLD, // in MPI_Comm Communicator
&my_rank // out int ID of the processor
);
// Gets the number of processors in the network.
MPI_Comm_size ( // out int Error value
MPI_COMM_WORLD, // in MPI_Comm Communicator
&num_procs // out int Number of processors
);// Sends a message. Requires matching MPI_Recv.
// Blocking.
MPI_Send ( // out int Error value
buffer, // in void * Sending buffer
count, // in int Size of message in buffer
bufftype, // in MPI_Datatype Type of elems of msg
destination, // in int Destination processor ID
tag, // in int Message tag
comm // in MPI_Comm Communicator
);
// Receives a message. Requires matching MPI_Send.
// Blocking
MPI_Recv ( // out int Error value
buffer, // out void * Receiving buffer
count, // in int Max num of elems in buffer
bufftype, // in MPI_Datatype Type of elems in buffer
source, // in int Source processor ID
tag, // in int Accepted message tag
comm // in MPI_Comm Communicator
status // out MPI_Status * Status
);
// Sends and receives a message, used to do ring communication without deadlock
// Blocking. Synchronous
MPI_Sendrecv( // out int Error value
sendbuf, // in void * Sending buffer
sendcount, // in int Size of msg in send buffer
sendtype, // in MPI_Datatype Type of elems in send buffer
dest, // in int Destination processor ID
sendtag, // in int Message tag
recvbuf, // out void * Receiving buffer
recvcount, // in int Size of msg in receive buffer
recvtype, // in MPI_Datatype Type of elems in receive buffer
source, // in int Source processor ID
recvtag, // in int Accepted message tag
comm, // in MPI_Comm Communicator
status // out MPI_Status * Status
);
// Blocks until all processes reach this point.
// Blocking. Synchronized.
MPI_Barrier( // out int Error value
comm // in MPI_Comm Communicator
)// Broadcasts a message from one proc to all others.
// Blocking. Synchronized.
MPI_Bcast( // out int Error value
buffer, // i/o void * Send/Receive buffer
count, // in int Buffer size
recvtype, // in MPI_Datatype Type of message (see appendix)
root, // in int Broadcaster processor ID
comm // in MPI_Comm Communicator
);
// Splits a message evenly for all processors in the network
// NOTE: sendbuf size should be at least sendcount * num_procs
// Blocking. Synchronized.
MPI_Scatter( // out int Error value
sendbuf, // in void * Send buffer
sendcount, // in int Num of elems for each processor
sendtype, // in MPI_Datatype Type of elems to send
recvbuf, // out void * Receive buffer
recvcount, // in int Num of elems sent (=sendcount)
recvtype, // in MPI_Datatype Type of elems sent (=sendtype)
root, // in int Scatterer processor ID
comm // in MPI_Comm Communicator
);
// Assembles a message from pieces from all processors
// NOTE: recvbuf size should be at least recvcount * num_procs
// Blocking. Synchronized.
MPI_Gather( // out int Error value
sendbuf, // in void * Send buffer
sendcount, // in int Num of elems in each processor
sendtype, // in MPI_Datatype Type of elems to send
recvbuf, // out void * Receive buffer
recvcount, // in int Num of elems sent (=sendcount)
recvtype, // in MPI_Datatype Type of elems sent (=sendtype)
root, // in int Gatherer processor ID
comm // in MPI_Comm Communicator
);
// Same as MPI_Gather, but all processors get the output
// NOTE: recvbuf size should be at least recvcount * num_procs
// Blocking. Synchronized.
MPI_Allgather( // out int Error value
sendbuf, // in void * Send buffer
sendcount, // in int Num of elems in each processor
sendtype, // in MPI_Datatype Type of elems to send
recvbuf, // out void * Receive buffer
recvcount, // in int Num of elems sent (=sendcount)
recvtype, // in MPI_Datatype Type of elems sent (=sendtype)
comm // in MPI_Comm Communicator
);
// Splits a message in pieces of different size and offset
// Blocking. Synchronized.
MPI_Scatterv( // out int Error value
sendbuf, // in void * Send buffer
sendcounts, // in int * Sizes of msgs for each proc
displs, // in int * Offsets of msgs for each proc
sendtype, // in MPI_Datatype Type of elems to send
recvbuf, // out void * Receive buffer
recvcount, // in int Count to receive in this proc
recvtype, // in MPI_Datatype Type of elems to receive
root, // in int Scatterer processor ID
comm // in MPI_Comm Communicator
);
// Gathers a message from pieces of different size and offset
// Blocking. Synchronized.
MPI_Gatherv( // out int Error value
sendbuf, // in void * Send buffer
sendcount, // in int Count to send from this proc
sendtype, // in MPI_Datatype Type of elems to send
recvbuf, // out void * Receive buffer
recvcounts, // in int * Sizes of msgs from each proc
displs, // in int * Offsets of msgs from each proc
recvtype, // in MPI_Datatype Type of elems to receive
root, // in int Gatherer processor ID
comm // in MPI_Comm Communicator
);// Applies an operation to values across all processors, producing a single
// value in a single processor
// NOTE: If an array is passed as input, operation is performed element-wise
// That is, the Max of all elements in index 1, and the max of all elems
// in index 2, and so on.
// Blocking. Synchronized.
MPI_Reduce( // out int Error value
sendbuf, // in void * Send buffer
recvbuf, // out void * Receive buffer
count, // in int Num of elems sent by each proc
datatype, // in MPI_Datatype Type of elems sent/received
op, // in MPI_Op Operation to perform (see appendix)
root, // in int Receiving processor ID
comm // in MPI_Comm Communicator
);
// Same as before, but all processors get the output
// NOTE: If an array is passed as input, operation is performed element-wise
// That is, the Max of all elements in index 1, and the max of all elems
// in index 2, and so on.
// Blocking. Synchronized.
MPI_Allreduce( // out int Error value
sendbuf, // in void * Send buffer
recvbuf, // out void * Receive buffer
count, // in int Num of elems sent by each proc
datatype, // in MPI_Datatype Type of elems sent/received
op, // in MPI_Op Operation to perform (see appendix)
comm // in MPI_Comm Communicator
);