Blocking Sends

• Argument Definitions

  IN = provided by programmer, OUT = set by routine

  buf: starting address of message buffer (IN)
  count: number of elements in message (IN)
  datatype: type of elements in message (IN)
  dest: rank of destination task in communicator comm (IN)
  tag: message tag (IN)
  comm: communicator (IN)
  ierror: error code (OUT)

• Blocking Synchronous Send

  C

  int MPI_Ssend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm)

  Fortran

  MPI_Ssend (buf, count, datatype, dest, tag, comm, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, ierror

• Blocking Ready Send

  C

  int MPI_Rsend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm)

  Fortran

  MPI_Rsend (buf, count, datatype, dest, tag, comm, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, ierror

• Blocking Buffered Send

  C

  int MPI_Bsend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm)

  Fortran

  MPI_Bsend (buf, count, datatype, dest, tag, comm, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, ierror

• Blocking Standard Send

  C

  int MPI_Send (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm)

  Fortran

  MPI_Send (buf, count, datatype, dest, tag, comm, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, ierror

---

Blocking Receive

• Argument Definitions

  IN = provided by programmer, OUT = set by routine

  buf: starting address of message buffer (OUT-buffer contents written)
  count: number of elements in message (IN)
  datatype: type of elements in message (IN)
  source: rank of source task in communicator comm (IN)
  tag: message tag (IN)
  comm: communicator (IN)
  status: status of communication event (OUT)
  ierror: error code (OUT)

• C

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

• Fortran

  MPI_Recv (buf, count, datatype, source, tag, comm, status, ierror)
  <type> buf(*)
  integer count, datatype, source, tag, comm, status(MPI_STATUS_SIZE), ierror

---

Non-blocking Sends

• Argument Definitions

  IN = provided by programmer, OUT = set by routine

  buf: starting address of message buffer (IN)
  count: number of elements in message (IN)
  datatype: type of elements in message (IN)
  dest: rank of destination task in communicator comm (IN)
  tag: message tag (IN)
  comm: communicator (IN)
  request: identifies a communication event (OUT)
  ierror: error code (OUT)

• Non-blocking Synchronous Send

  C

  int MPI_Issend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm, MPI_Request *request)

  Fortran

  MPI_Issend (buf, count, datatype, dest, tag, comm, request, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, request, ierror

• Non-blocking Ready Send

  C

  int MPI_Irsend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm, MPI_Request *request)

  Fortran

  MPI_Irsend (buf, count, datatype, dest, tag, comm, request, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, request, ierror

• Non-blocking Buffered Send

  C

  int MPI_Ibsend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm, MPI_Request *request)

  Fortran

  MPI_Ibsend (buf, count, datatype, dest, tag, comm, request, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, request, ierror

• Non-blocking Standard Send

  C

  int MPI_Isend (void *buf, int count, MPI_Datatype datatype, int dest, int tag, MPI_Comm comm, MPI_Request *request)

  Fortran

  MPI_Isend (buf, count, datatype, dest, tag, comm, request, ierror)
  <type> buf(*)
  integer count, datatype, dest, tag, comm, request, ierror

---

Non-blocking Receive

• Argument Definitions

  IN = provided by programmer, OUT = set by routine

  buf: starting address of message buffer (OUT-buffer contents written)
  count: number of elements in message (IN)
  datatype: type of elements in message (IN)
  source: rank of source task in communicator comm (IN)
  tag: message tag (IN)
  comm: communicator (IN)
  request: identifies a communication event (OUT)
  ierror: error code (OUT)

• C

  int MPI_Irecv (void* buf, int count, MPI_Datatype datatype, int source, int tag, MPI_Comm comm, MPI_Request *request)

• Fortran

  MPI_Irecv (buf, count, datatype, source, tag, comm, request, ierror)
  <type> buf(*)
  integer count, datatype, source, tag, comm, request, ierror

---

Managing the User-Supplied Buffer

• Attaching the Buffer

  Argument Definitions

  buf: starting address of user-supplied buffer (IN)
  size: number of bytes in user supplied buffer (IN)
  ierror: error code (OUT)

  C

  int MPI_Buffer_attach (void* buf, int size)

  Fortran

  MPI_Buffer_attach (buf, size, ierror)
  <type> buf(*)
  integer size, ierror

• Detaching the Buffer

  Argument Definitions

  buf: starting address of user-supplied buffer (OUT)
  size: number of bytes in user supplied buffer (OUT)
  ierror: error code (OUT)

  C

  int MPI_Buffer_detach (void** buf, int* size)

  Fortran

  MPI_Buffer_detach (buf, size, ierror)
  <type> buf(*)
  integer size, ierror

---

Checking for Completion, Blocking

• Argument Definitions

  request: identifies a communication event (INOUT)
  status: status of communication event (OUT)
  count: number of communication events (IN)
  index: index in array of requests of completed event (OUT)
  incount: number of communication events (IN)
  outcount: number of completed events (OUT)
  ierror: error code (OUT)

• C

  int MPI_Wait (MPI_Request *request, MPI_Status *status)

  int MPI_Waitall (int count, MPI_Request *array_of_requests, MPI_Status *array_of_statuses)

  int MPI_Waitany (int count, MPI_Request *array_of_requests, int *index, MPI_Status *status)

  int MPI_Waitsome (int incount, MPI_Request *array_of_requests, int *outcount, int* array_of_indices, MPI_Status *array_of_statuses)

• Fortran

  MPI_Wait (request, status, ierror)
  integer request, status(MPI_STATUS_SIZE), ierror

  MPI_Waitall (count, array_of_requests, array_of_statuses, ierror)
  integer count, array_of_requests(*), array_of_statuses(MPI_STATUS_SIZE,*), ierror

  MPI_Waitany (count, array_of_requests, index, status, ierror)
  integer count, array_of_requests(*), index, status(MPI_STATUS_SIZE), ierror

  MPI_Waitsome (incount, array_of_requests, outcount, array_of_indices, array_of_statuses, ierror)
  integer incount, array_of_requests(*), outcount, array_of_indices(*), array_of_statuses(MPI_STATUS_SIZE,*), ierror

---

Checking for Completion, Non-Blocking

• Argument Definitions

  request: identifies a communication event (INOUT)
  flag: TRUE if communication event has completed (OUT)
  status: status of communication event (OUT)
  count: number of communication events (IN)
  index: index in array of requests of completed event (OUT)
  incount: number of communication events (IN)
  outcount: number of completed events (OUT)
  ierror: error code (OUT)

• C

  int MPI_Test (MPI_Request *request, int *flag, MPI_Status *status)

  int MPI_Testall (int count, MPI_Request *array_of_requests, int *flag, MPI_Status *array_of_statuses)

  int MPI_Testany (int count, MPI_Request *array_of_requests, int *index, int *flag, MPI_Status *status)

  int MPI_Testsome (int incount, MPI_Request *array_of_requests, int *outcount, int* array_of_indices, MPI_Status *array_of_statuses)

• Fortran

  MPI_Test (request, flag, status, ierror)
  integer request, status(MPI_STATUS_SIZE), ierror
  logical flag

  MPI_Testall (count, array_of_requests, flag, array_of_statuses, ierror)
  integer count, array_of_requests(*), array_of_statuses(MPI_STATUS_SIZE,*), ierror
  logical flag

  MPI_Testany (count, array_of_requests, index, flag, status, ierror)
  integer count, array_of_requests(*), index, status(MPI_STATUS_SIZE), ierror
  logical flag

  MPI_Testsome (incount, array_of_requests, outcount, array_of_indices, array_of_statuses, ierror)
  integer incount, array_of_requests(*), outcount, array_of_indices(*), array_of_statuses(MPI_STATUS_SIZE,*), ierror

---

Miscellaneous

• Combined Send/Recv

  Argument Definitions

  sendbuf: starting address of send buffer (IN)
  sendcount: number of elements in outgoing message (IN)
  sendtype: type of elements in outgoing message (IN)
  dest: rank in communicator of destination task (IN)
  sendtag: message tag for outgoing communication (IN)
  recvbuf: starting address of receive buffer (OUT-buffer contents written)
  recvcount: number of elements in incoming message (IN)
  recvtype: type of elements in incoming message (IN)
  source: rank in communicator of source task (IN)
  recvtag: message tag for incoming communication (IN)
  comm: communicator (IN)
  status: status of communication event (OUT)
  buf: starting address of send and receive buffers (INOUT)
  ierror: error code (OUT)

  C

  int MPI_Sendrecv (void *sendbuf, int sendcount, MPI_Datatype sendtype, int dest, int sendtag, void *recvbuf, int recvcount, MPI_Datatype recvtype, int source, int recvtag, MPI_Comm comm, MPI_Status *status)

  int MPI_Sendrecv_replace (void *buf, int count, MPI_Datatype datatype, int dest, int sendtag, int source, int recvtag, MPI_Comm comm, MPI_Status *status)

  Fortran

  MPI_Sendrecv (sendbuf, sendcount, sendtype, dest, sendtag, recvbuf, recvcount, recvtype, source, recvtag, comm, status, ierror)
  <type> sendbuf(*), recvbuf(*)
  integer sendcount, sendtype, dest, sendtag, recvcount, recvtype, source, recvtag, comm, status(MPI_STATUS_SIZE), ierror

  MPI_Sendrecv_replace (buf, count, datatype, dest, sendtag, source, recvtag, comm, status, ierror)
  <type> buf(*)
  integer count, datatype, dest, sendtag, source, recvtag, comm, status(MPI_STATUS_SIZE), ierror

• Probe

  Argument Definitions

  source: rank of source task in communicator comm (IN)
  tag: message tag (IN)
  comm: communicator (IN)
  status: status of communication event (OUT)
  flag: TRUE if message is available (OUT)
  ierror: error code (OUT)

  C

  int MPI_Probe (int source, int tag, MPI_Comm comm, MPI_Status *status)

  int MPI_Iprobe (int source, int tag, MPI_Comm comm, int *flag, MPI_Status *status)

  Fortran

  MPI_Probe (source, tag, comm, status, ierror)
  integer source, tag, comm, status(MPI_STATUS_SIZE), ierror

  MPI_Iprobe (source, tag, comm, flag, status, ierror)
  integer source, tag, comm, status(MPI_STATUS_SIZE), ierror
  logical flag

• Status parameters

             FORTRAN                   C
             -------                   -
  source: status(MPI_SOURCE)  status.MPI_SOURCE
  tag:    status(MPI_TAG)     status.MPI_TAG
  error:  status(MPI_ERROR)   status.MPI_ERROR
  

• Learn the number of elements

  Argument Definitions

  status: status of communication event (IN)
  count: number of elements in message (OUT)
  datatype: type of elements in message (IN)

  C

  int MPI_Get_count (MPI_Status *status, MPI_Datatype datatype, int *count)

  Fortran

  MPI_Get_count (status, datatype, count, ierror)
  integer status(MPI_STATUS_SIZE), datatype, count, ierror

---

References

William Gropp, Ewing Lusk and Anthony Skjellum (1999). Using MPI: Portable Parallel Programming with the Message-Passing Interface, Second Edition. The MIT Press, Cambridge, Massachusetts.

Message Passing Interface Forum (1995). MPI: A Message Passing Interface Standard. June 12, 1995. This is the MPI version 1.1 standard. It (and more recent documents) is available from http://www.mpi-forum.org/docs/docs.html.

Marc Snir, Steve Otto, Steven Huss-Lederman, David Walker, and Jack Dongarra (1996).  MPI: The Complete Reference. The MIT Press, Cambridge, Massachusetts. This book is basically an elaboration of the standard document.  The complete book is available online at http://www.netlib.org/utk/papers/mpi-book/mpi-book.html.

An overall good reference site is http://www-unix.mcs.anl.gov/mpi/index.html.