The R Project SVN R

% File src/library/parallel/man/makePSOCKcluster.Rd

% Part of the R package, https://www.R-project.org

% Copyright 2003-2018 R Core Team

% Distributed under GPL 2 or later

\name{makeCluster}

\alias{makeCluster}

\alias{makePSOCKcluster}

\alias{makeForkCluster}

\alias{stopCluster}

\alias{setDefaultCluster}

\alias{getDefaultCluster}

\alias{R_PARALLEL_PORT}

\title{

  Create a Parallel Socket Cluster

}

\description{

  Creates a set of copies of \R running in parallel and communicating

  over sockets.

}

\usage{

makeCluster(spec, type, ...)

makePSOCKcluster(names, ...)

makeForkCluster(nnodes = getOption("mc.cores", 2L), ...)

stopCluster(cl = NULL)

setDefaultCluster(cl = NULL)

getDefaultCluster()

}

\arguments{

  \item{spec}{A specification appropriate to the type of cluster.}

  \item{names}{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 \samp{localhost}).}

  \item{nnodes}{The number of nodes to be forked.}

  \item{type}{One of the supported types: see \sQuote{Details}.}

  \item{\dots}{Options to be passed to the function spawning the workers.

    See \sQuote{Details}.}

  \item{cl}{an object of class \code{"cluster"}.}

}

\details{

  \code{makeCluster} creates a cluster of one of the supported types.

  The default type, \code{"PSOCK"}, calls \code{makePSOCKcluster}.  Type

  \code{"FORK"} calls \code{makeForkCluster}.  Other types are passed to

  package \CRANpkg{snow}.

  \code{makePSOCKcluster} is an enhanced version of

  \code{makeSOCKcluster} in package \CRANpkg{snow}.  It runs

  \command{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).

  \code{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 \code{makePSOCKcluster}):

  \describe{

    \item{\code{master}}{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 \samp{somename.local}, a name known only to itself.}

    \item{\code{port}}{The port number for the socket connection,

      default taken from the environment variable \env{R_PARALLEL_PORT},

      then a randomly chosen port in the range \code{11000:11999}.}

    \item{\code{setup_timeout}}{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.}

    \item{\code{timeout}}{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).}

    \item{\code{outfile}}{Where to direct the \code{\link{stdout}} and

      \code{\link{stderr}} connection output from the workers.

      \code{""} indicates no redirection (which may only be useful for

      workers on the local machine).

      Defaults to \file{/dev/null} (\file{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.}

    \item{\code{homogeneous}}{Logical.  Are all the hosts running

      identical setups, so \command{Rscript} can be launched using

      the same path on each?  Otherwise \command{Rscript} has to be in

      the default path on the workers.}

    \item{\code{rscript}}{The path to \command{Rscript} on the workers,

      used if \code{homogeneous} is true. Defaults to the full path on

      the master.}

    \item{\code{rscript_args}}{Character vector of additional

      arguments for \command{Rscript} such as \option{--no-environ}.}

    \item{\code{renice}}{A numerical \sQuote{niceness} to set for the

      worker processes, e.g.\sspace{}\code{15} for a low priority.

      OS-dependent: see \code{\link{psnice}} for details.}

    \item{\code{rshcmd}}{The command to be run on the master to launch a

      process on another host.  Defaults to \command{ssh}.}

    \item{\code{user}}{The user name to be used when communicating with

      another host.}

    \item{\code{manual}}{Logical.  If true the workers will need to be

      run manually.}

    \item{\code{methods}}{Logical.  If true (default) the workers will

      load the \pkg{methods} package: not loading it saves ca 30\% of the

      startup CPU time of the cluster.}

    \item{\code{useXDR}}{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.}

  }

  Function \code{makeForkCluster} creates a socket cluster by forking

  (and hence is not available on Windows).  It supports options

  \code{port}, \code{timeout} and \code{outfile}, and always uses

  \code{useXDR = FALSE}. It is \emph{strongly discouraged} to use the

  \code{"FORK"} cluster with GUI front-ends  or multi-threaded libraries.

#ifdef unix

  See \code{\link{mcfork}} for details.

#endif

  It is good practice to shut down the workers by calling

  \code{\link{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 \code{setDefaultCluster} registers a cluster as the default one

  for the current session.  Using \code{setDefaultCluster(NULL)} removes

  the registered cluster, as does stopping that cluster.

}

\value{

  For the cluster creators, an object of class

  \code{c("SOCKcluster", "cluster")}.

  For the default cluster setter and getter, the registered default

  cluster or \code{NULL} if there is no such cluster.

}

\author{

  Luke Tierney and R Core.

  Derived from the \CRANpkg{snow} package.

}