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
makeCluster creates a cluster of one of the supported types.
The default type,
makeForkCluster. Other types are passed to
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
The 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.
The port number for the socket connection,
default taken from the environment variable R_PARALLEL_PORT,
then a randomly chosen port in the range
The 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).
The 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.
Where to direct the
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
Logical, default true. See ‘Note’.
Character vector of additional
Rscript such as --no-environ.
A numerical ‘niceness’ to set for the
worker processes, e.g.
15 for a low priority.
psnice for details.
The command to be run on the master to launch a
process on another host. Defaults to
The user name to be used when communicating with another host.
Logical. If true the workers will need to be run manually.
Logical. If true (default) the workers will load the methods package: not loading it saves ca 30% of the startup CPU time of the cluster.
Logical. 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.
workers will be started in parallel during cluster setup when this is
possible, which is now for homogeneous
"PSOCK" clusters with
all workers started automatically (
manual = FALSE) on the local
machine. Workers will be started sequentially on other clusters, on
all clusters with
setup_strategy = "sequential" and on R 3.6.0
and older. This option is for expert use only (e.g. debugging) and
may be removed in future versions of R.
makeForkCluster creates a socket cluster by forking
(and hence is not available on Windows). It supports options
outfile, and always uses
useXDR = FALSE. It is strongly discouraged to use the
"FORK" cluster with GUI front-ends or multi-threaded libraries.
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).
setDefaultCluster registers a cluster as the default one
for the current session. Using
the registered cluster, as does stopping that cluster.
For the cluster creators, an object of class
For the default cluster setter and getter, the registered default
NULL if there is no such cluster.
homogeneous = TRUE was for years documented as
‘Are all the hosts running identical setups?’, but this was
apparently more restrictive than its author intended and not required
by the code.
The current interpretation of
homogeneous = TRUE is that
Rscript can be launched using the same path on each worker.
That path is given by the option
rscript and defaults to the
full path to
Rscript on the master. (The workers are not
required to be running the same version of R as the master, nor even
as each other.)
homogeneous = FALSE,
Rscript on the workers is
found on their default shell's path.
For the very common usage of running both master and worker on a single multi-core host, the default settings are the appropriate ones.
Luke Tierney and R Core.
Derived from the snow package.
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