Creates a set of copies of R running in parallel and communicating over sockets.
makeCluster(spec, type, ...)
makePSOCKcluster(names, ...)
makeForkCluster(nnodes = getOption("mc.cores", 2L), ...)stopCluster(cl = NULL)
setDefaultCluster(cl = NULL)
getDefaultCluster()
A specification appropriate to the type of cluster.
Either a character vector of host names on which to run the worker copies of R, or a positive integer (in which case that number of copies is run on localhost).
The number of nodes to be forked.
One of the supported types: see ‘Details’.
Options to be passed to the function spawning the workers. See ‘Details’.
an object of class "cluster".
For the cluster creators, an object of class
c("SOCKcluster", "cluster").
For the default cluster setter and getter, the registered default
cluster or NULL if there is no such cluster.
makeCluster creates a cluster of one of the supported types.
The default type, "PSOCK", calls makePSOCKcluster. Type
"FORK" calls makeForkCluster. Other types are passed to
package snow.
makePSOCKcluster is an enhanced version of
makeSOCKcluster in package snow. It runs
Rscript on the specified host(s) to set up a worker process
which listens on a socket for expressions to evaluate, and returns the
results (as serialized objects).
makeForkCluster is merely a stub on Windows. On Unix-alike
platforms it creates the worker process by forking.
The workers are most often running on the same host as the master, when no options need be set.
Several options are supported (mainly for makePSOCKcluster):
masterThe host name of the master, as known to the workers. This may not be the same as it is known to the master, and on private subnets it may be necessary to specify this as a numeric IP address. For example, macOS is likely to detect a machine as somename.local, a name known only to itself.
portThe port number for the socket connection,
default taken from the environment variable R_PARALLEL_PORT,
then a randomly chosen port in the range 11000:11999.
setup_timeoutThe maximum number of seconds a worker attempts to connect to master before failing. Default is 2 minutes. The waiting time before the next attempt starts at 0.1 seconds and is incremented 50% after each retry.
timeoutThe timeout in seconds for that port. This is the maximum time of zero communication between master and worker before failing. Default is 30 days (and the POSIX standard only requires values up to 31 days to be supported).
outfileWhere to direct the stdout and
stderr connection output from the workers.
"" indicates no redirection (which may only be useful for
workers on the local machine).
Defaults to /dev/null (nul: on Windows). The other
possibility is a file path on the worker's host.
Files will be opened in append mode, as all workers log to the
same file.
homogeneousLogical. Are all the hosts running
identical setups, so Rscript can be launched using
the same path on each? Otherwise Rscript has to be in
the default path on the workers.
rscriptThe path to Rscript on the workers,
used if homogeneous is true. Defaults to the full path on
the master.
rscript_argsCharacter vector of additional
arguments for Rscript such as --no-environ.
reniceA numerical ‘niceness’ to set for the
worker processes, e.g.15 for a low priority.
OS-dependent: see psnice for details.
rshcmdThe command to be run on the master to launch a
process on another host. Defaults to ssh.
userThe user name to be used when communicating with another host.
manualLogical. If true the workers will need to be run manually.
methodsLogical. If true (default) the workers will load the methods package: not loading it saves ca 30% of the startup CPU time of the cluster.
useXDRLogical. If true (default) serialization will use XDR: where large amounts of data are to be transferred and all the nodes are little-endian, communication may be substantially faster if this is set to false.
Function makeForkCluster creates a socket cluster by forking
(and hence is not available on Windows). It supports options
port, timeout and outfile, and always uses
useXDR = FALSE. It is strongly discouraged to use the
"FORK" cluster with GUI front-ends or multi-threaded libraries.
See mcfork for details.
It is good practice to shut down the workers by calling
stopCluster: however the workers will terminate
themselves once the socket on which they are listening for commands
becomes unavailable, which it should if the master R session is
completed (or its process dies).
Function setDefaultCluster registers a cluster as the default one
for the current session. Using setDefaultCluster(NULL) removes
the registered cluster, as does stopping that cluster.