mpi.send | R Documentation |
The pair mpi.send
and mpi.recv
are two most used blocking
calls for point-to-point communications. An int, double or char vector
can be transmitted from any source to any destination.
The pair mpi.isend
and mpi.irecv
are the same except that
they are nonblocking calls.
Blocking and nonblocking calls are interchangeable, e.g., nonblocking sends can be matched with blocking receives, and vice-versa.
mpi.send(x, type, dest, tag, comm = 1)
mpi.isend(x, type, dest, tag, comm = 1, request=0)
mpi.recv(x, type, source, tag, comm = 1, status = 0)
mpi.irecv(x, type, source, tag, comm = 1, request = 0)
x |
data to be sent or received. Must be the same type for source and destination. The receive buffer must be as large as the send buffer. |
type |
1 for integer, 2 for double, and 3 for character. Others are not supported. |
dest |
the destination rank. Use |
source |
the source rank. Use |
tag |
non-negative integer. Use |
comm |
a communicator number. |
request |
a request number. |
status |
a status number. |
The pair mpi.send
(or mpi.isend
) and mpi.recv
(or mpi.irecv
) must be used together, i.e., if there is a sender,
then there must be a receiver. Any mismatch will result a deadlock
situation, i.e., programs stop responding. The receive buffer must be
large enough to contain an incoming message otherwise programs will be
crashed. One can use mpi.probe
(or mpi.iprobe) and
mpi.get.count
to find the length of an incoming message
before calling mpi.recv
. If mpi.any.source
or
mpi.any.tag
is used in mpi.recv
, one can use
mpi.get.sourcetag
to find out the source or tag of the
received message. To send/receive an R object rather than an int, double
or char vector, please use the pair mpi.send.Robj
and
mpi.recv.Robj
.
Since mpi.irecv
is a nonblocking call, x
with enough buffer
must be created before using it. Then use nonblocking completion calls
such as mpi.wait
or mpi.test
to test if
x
contains data from sender.
If multiple nonblocking sends or receives are used, please use request
number consecutively from 0. For example, to receive two messages from two
slaves, try
mpi.irecv(x,1,source=1,tag=0,comm=1,request=0)
mpi.irecv(y,1,source=2,tag=0,comm=1,request=1)
Then mpi.waitany
, mpi.waitsome
or mpi.waitall
can be
used to complete the operations.
mpi.send
and mpi.isend
return no value. mpi.recv
returns the int, double or char vector sent from source
. However,
mpi.irecv
returns no value. See details for explanation.
Hao Yu
mpi.send.Robj
,
mpi.recv.Robj
,
mpi.probe
,
mpi.wait
,
mpi.get.count
,
mpi.get.sourcetag
.
#on a slave
#mpi.send(1:10,1,0,0)
#on master
#x <- integer(10)
#mpi.irecv(x,1,1,0)
#x
#mpi.wait()
#x
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