## 3.7.2. Communication initiation

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We use the same naming conventions as for blocking communication: a prefix of B, S, or R is used for buffered, synchronous or ready mode. In addition a prefix of I (for immediate) indicates that the call is nonblocking.

MPI_ISEND(buf, count, datatype, dest, tag, comm, request)
[ IN buf] initial address of send buffer (choice)
[ IN count] number of elements in send buffer (integer)
[ IN datatype] datatype of each send buffer element (handle)
[ IN dest] rank of destination (integer)
[ IN tag] message tag (integer)
[ IN comm] communicator (handle)
[ OUT request] communication request (handle)

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

`MPI_ISEND(BUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR
`

Start a standard mode, nonblocking send.

MPI_IBSEND(buf, count, datatype, dest, tag, comm, request)
[ IN buf] initial address of send buffer (choice)
[ IN count] number of elements in send buffer (integer)
[ IN datatype] datatype of each send buffer element (handle)
[ IN dest] rank of destination (integer)
[ IN tag] message tag (integer)
[ IN comm] communicator (handle)
[ OUT request] communication request (handle)

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

`MPI_IBSEND(BUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR
`

Start a buffered mode, nonblocking send.

MPI_ISSEND(buf, count, datatype, dest, tag, comm, request)
[ IN buf] initial address of send buffer (choice)
[ IN count] number of elements in send buffer (integer)
[ IN datatype] datatype of each send buffer element (handle)
[ IN dest] rank of destination (integer)
[ IN tag] message tag (integer)
[ IN comm] communicator (handle)
[ OUT request] communication request (handle)

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

`MPI_ISSEND(BUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR
`

Start a synchronous mode, nonblocking send.

MPI_IRSEND(buf, count, datatype, dest, tag, comm, request)
[ IN buf] initial address of send buffer (choice)
[ IN count] number of elements in send buffer (integer)
[ IN datatype] datatype of each send buffer element (handle)
[ IN dest] rank of destination (integer)
[ IN tag] message tag (integer)
[ IN comm] communicator (handle)
[ OUT request] communication request (handle)

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

`MPI_IRSEND(BUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR
`

Start a ready mode nonblocking send.

MPI_IRECV (buf, count, datatype, source, tag, comm, request)
[ OUT buf] initial address of receive buffer (choice)
[ IN count] number of elements in receive buffer (integer)
[ IN datatype] datatype of each receive buffer element (handle)
[ IN source] rank of source (integer)
[ IN tag] message tag (integer)
[ IN comm] communicator (handle)
[ OUT request] communication request (handle)

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

`MPI_IRECV(BUF, COUNT, DATATYPE, SOURCE, TAG, COMM, REQUEST, IERROR)
<type> BUF(*)
INTEGER COUNT, DATATYPE, SOURCE, TAG, COMM, REQUEST, IERROR
`

Start a nonblocking receive.

These calls allocate a communication request object and associate it with the request handle (the argument request). The request can be used later to query the status of the communication or wait for its completion.

A nonblocking send call indicates that the system may start copying data out of the send buffer. The sender should not access any part of the send buffer after a nonblocking send operation is called, until the send completes.

A nonblocking receive call indicates that the system may start writing data into the receive buffer. The receiver should not access any part of the receive buffer after a nonblocking receive operation is called, until the receive completes.

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MPI-1.1 of June 12, 1995
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