makeCluster starts a cluster of the specified or default type
and returns a reference to the cluster. Supported cluster types are
"SOCK",
"MPI", and "NWS". For
"MPI" clusters the spec argument should be an integer
specifying the number of slave nodes to create. For "SOCK" and
"NWS"
clusters spec should be a character vector naming the hosts on
which slave nodes should be started; one node is started for each
element in the vector. For "SOCK" and "NWS" clusters
spec can also be an integer specifying the
number of slaves nodes to create on the local machine.
For SOCK and NWS clusters the spec can also be a
list of machine specifications, each a list of named option values.
Such a list must include a character value named host host
specifying the name or address of the host to use. Any other option
can be specified as well. For SOCK and NWS clusters
this may be a more convenient alternative than inhomogeneous cluster
startup procedure. The options rscript and snowlib are
often useful; see the examples below.
stopCluster should be called to properly shut down the cluster
before exiting R. If it is not called it may be necessary to use
external means to ensure that all slave processes are shut down.
setDefaultClusterOptions can be used to specify alternate
values for default cluster options. There are many options. The
most useful ones are type and homogeneous. The
default value of the type option is currently set to
"MPI" if Rmpi is on the search path. Otherwise it is set to
"MPI"
if Rmpi is available,
and to "SOCK" otherwise.
The homogeneous option should be set to FALSE to
specify that the startup procedure for inhomogeneous clusters is to
be used; this requires some additional configuration. The default
setting is TRUE unless the environment variable
R_SNOW_LIB is defined on the master host with a non-empty
value.
The optionoutfile can be used to specify the file to which
slave node output is to be directed. The default is /dev/null;
during debugging of an installation it can be useful to set this to a
proper file. On some systems setting outfile to "" or
to /dev/tty will result in worker output being sent tothe
terminal running the master process.
The functions makeSOCKcluster,
makeMPIcluster, and makeNWScluster can be used to start
a cluster of the corresponding type.
In MPI configurations where process spawning is not available and
something like mpirun is used to start a master and a set of slaves
the corresponding cluster will have been pre-constructed and can be obtained
with getMPIcluster. It is also possible to obtain a reference
to the running cluster using makeCluster or
makeMPIcluster. In this case the count argument can be
omitted; if it is supplied, it must equal the number of nodes in the
cluster. This interface is still experimental and
subject to change.
For SOCK and NWS clusters the option manual = TRUE forces a
manual startup mode in which the master prints the command to be run
manually to start a worker process. Together with setting the
outfile option this can be useful for debugging cluster startup.
## Not run:
## Two workers run on the local machine as a SOCK cluster.
cl <- makeCluster(c("localhost","localhost"), type = "SOCK")
clusterApply(cl, 1:2, get("+"), 3)
stopCluster(cl)
## Another approach to running on the local machine as a SOCK cluster.
cl <- makeCluster(2, type = "SOCK")
clusterApply(cl, 1:2, get("+"), 3)
stopCluster(cl)
## A SOCK cluster with two workers on Mac OS X, two on Linux, and two
## on Windows:
macOptions <-
list(host = "owasso",
rscript = "/Library/Frameworks/R.framework/Resources/bin/Rscript",
snowlib = "/Library/Frameworks/R.framework/Resources/library")
lnxOptions <-
list(host = "itasca",
rscript = "/usr/lib64/R/bin/Rscript",
snowlib = "/home/luke/tmp/lib")
winOptions <-
list(host="192.168.1.168",
rscript="C:/Program Files/R/R-2.7.1/bin/Rscript.exe",
snowlib="C:/Rlibs")
cl <- makeCluster(c(rep(list(macOptions), 2), rep(list(lnxOptions), 2),
rep(list(winOptions), 2)), type = "SOCK")
clusterApply(cl, 1:6, get("+"), 3)
stopCluster(cl)
## End(Not run)