MPI Subroutine Synopses

The subroutines described here are those only used in the examples, not exhaustive.

mpi_address(location,address,ierr)

• [void*], intent(in) :: location : location of data (any datatypes)
• integer, intent(out) :: address : byte address
• integer, intent(out) :: ierr : error code

Gets a byte address of location.

mpi_bcast(buf,count,datatype,root,comm,ierr)

• datatype, intent(inout) :: buf : starting location of data to be broadcasted
• integer, intent(in) :: count : number of data to be broadcasted
• integer, intent(in) :: datatype : type of data to be broadcasted
• integer, intent(in) :: root : rank of the processor which broadcasts data
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: ierr : error code

The root processor broadcasts buf to all processors in the communicator, and all other processors in the communicator store the received data into buf.

mpi_comm_rank(comm,rank,ierr)

• integer, intent(in) :: comm : communicator
• integer, intent(out) :: rank : processor rank
• integer, intent(out) :: ierr : error code

Gets a rank of processor.

mpi_comm_size(comm,size,ierr)

• integer, intent(in) :: comm : communicator
• integer, intent(out) :: size : number of processors
• integer, intent(out) :: ierr : error code

Gets the number of processors in the communicator.

mpi_finalize(ierr)

• integer, intent(out) :: ierr : error code

Finalizes MPI. MPI subroutines should be called before this statement.

mpi_gather(sendbuf,sendcounts,sendtype,recvbuf,recvcounts,recvtype,root,comm,ierr)

• sendtype, intent(in) :: sendbuf : starting location of data to be sent by each processor
• integer, intent(in) :: sendcounts : number of data to be sent by each processor
• integer, intent(in) :: sendtype : type of data to be sent by each processor
• recvtype, intent(out) :: recvbuf : starting location of data to be received by the root processor
• integer, intent(in) :: recvcounts : number of data sent from each processor to be received by the root processor
• integer, intent(in) :: recvtype : type of data to be received by the root processor
• integer, intent(in) :: root : rank of processor to which data are gathered
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: ierr : error code

Gathers the data sent by each processor to the root processor. The data sent by I_p-th processor are stored to the location next to the location of the data sent by the (I_p-1)-th processor. Sendcounts/sendtype and recvcounts/recvtype should be the same for all processors.

mpi_init(ierr)

• integer, intent(out) :: ierr : error code

Initializes MPI. MPI subroutines should be called after this statement.

mpi_irecv(buf,count,datatype,source,tag,comm,request,ierr)

• datatype, intent(out) :: buf : starting location of data to be received
• integer, intent(in) :: count : number of data to be received
• integer, intent(in) :: datatype : type of data to be received
• integer, intent(in) :: source : source processor rank
• integer, intent(in) :: tag : message tag
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: request : request tag to be used by mpi_wait
• integer, intent(out) :: ierr : error code

Non-blocking version of mpi_recv. Mpi_wait gets informations of the received data [status(mpi_status_size)] after it confirms data reception.

mpi_isend(buf,count,datatype,dest,tag,comm,request,ierr)

• datatype, intent(in) :: buf : starting location of data to be sent
• integer, intent(in) :: count : number of data to be sent
• integer, intent(in) :: datatype : type of data to be sent
• integer, intent(in) :: dest : destination processor rank
• integer, intent(in) :: tag : message tag
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: request : request tag to be used by mpi_wait
• integer, intent(out) :: ierr : error code

Non-blocking version of mpi_send.

mpi_recv(buf,count,datatype,source,tag,comm,status,ierr)

• datatype, intent(out) :: buf : starting location of data to be received
• integer, intent(in) :: count : number of data to be received
• integer, intent(in) :: datatype : type of data to be received
• integer, intent(in) :: source : source processor rank
• integer, intent(in) :: tag : message tag
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: status(mpi_status_size) : information of the received data
• integer, intent(out) :: ierr : error code

Receives the data sent from the source processor, and stores it into buf. The corresponding mpi_send should have the same message tag. Status(mpi_status_size) records informations of the received data, such as the source processor rank, the message tag, and the error code, etc.

mpi_reduce(operand,result,count,datatype,operator,root,comm,ierr)

• datatype, intent(in) :: operand : operand
• datatype, intent(out) :: result : result
• integer, intent(in) :: count : size of operand/result
• integer, intent(in) :: datatype : type of operand/result
• integer, intent(in) :: operator : operator
• integer, intent(in) :: root : rank of the processor which gets the result
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: ierr : error code

Operates operator on operands on each processor. An operator can be the predefined reduction operation (mpi_sum, mpi_max, mpi_min etc.) or a user defined operation.

mpi_send(buf,count,datatype,dest,tag,comm,ierr)

• datatype, intent(in) :: buf : starting location of data to be sent
• integer, intent(in) :: count : number of data to be sent
• integer, intent(in) :: datatype : type of data to be sent
• integer, intent(in) :: dest : destination processor rank
• integer, intent(in) :: tag : message tag
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: ierr : error code

Sends buf to the dest processor. The corresponding mpi_recv should have the same message tag.

mpi_sendrecv(sendbuf,sendcount,sendtype,dest,sendtag,recvbuf,recvcount,recvtype,source,recvtag,comm,status,ierr)

• sendtype, intent(in) :: sendbuf : starting location of data to be sent
• integer, intent(in) :: sendcount : number of data to be sent
• integer, intent(in) :: sendtype : type of data to be sent
• integer, intent(in) :: dest : destination processor rank
• integer, intent(in) :: sendtag : message tag
• recvtype, intent(out) :: recvbuf : starting location of data to be received
• integer, intent(in) :: recvcount : number of data to be received
• integer, intent(in) :: recvdatatype : type of data to be received
• integer, intent(in) :: source : source processor rank
• integer, intent(in) :: recvtag : message tag
• integer, intent(in) :: comm : communicator
• integer, intent(out) :: status(mpi_status_size) : information of the received data
• integer, intent(out) :: ierr : error code

Combination of mpi_send and mpi_recv.

mpi_type_commit(newtype,ierr)

• integer, intent(in) :: newtype : derivative type to be committed
• integer, intent(out) :: ierr : error code

Commits newtype. Newtype is available after committing.

mpi_type_struct((count,sizes,displacements,types,newtype,ierr)

• integer, intent(in) :: count : number of elements of newtype
• integer, intent(in) :: sizes(count) : size of each element of newtype
• integer, intent(in) :: displacements(count) : displacement of each element of newtype
• integer, intent(in) :: types(count) : datatype of each element of newtype
• integer, intent(out) :: newtype : new data type
• integer, intent(out) :: ierr : error code

Constructs a derivative type of the group of data defined by count, sizes, displacements, types.

mpi_wait(request,status,ierr)

• integer, intent(inout) :: request tag
• integer, intent(out) :: status(mpi_status_size) : informations of the data received by the corresponding non-blocking subroutine.
• integer, intent(out) :: ierr : error code

Waits until the corresponding non-blocking subroutine having the same request tag ends.