snow (version 0.4-4)

snow-startstop: Starting and Stopping SNOW Clusters

Description

Functions to start and stop a SNOW cluster and to set default cluster options.

Usage

makeCluster(spec, type = getClusterOption("type"), ...)
stopCluster(cl)
setDefaultClusterOptions(...)
makeSOCKcluster(names, ..., options = defaultClusterOptions)

makeMPIcluster(count, ..., options = defaultClusterOptions)

getMPIcluster()

Arguments

spec

cluster specification

count

number of nodes to create

names

character vector of node names

options

cluster options object

cl

cluster object

...

cluster option specifications

type

character; specifies cluster type.

Details

makeCluster starts a cluster of the specified or default type and returns a reference to the cluster. Supported cluster types are "SOCK", and "MPI". For "MPI" clusters the spec argument should be an integer specifying the number of worker nodes to create. For "SOCK" clusters spec should be a character vector naming the hosts on which worker nodes should be started; one node is started for each element in the vector. For "SOCK" clusters spec can also be an integer specifying the number of worker nodes to create on the local machine.

For SOCK 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 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 worker 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 worker 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, and makeMPIcluster 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 workers 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 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.

For more details see https://stat.uiowa.edu/~luke/R/cluster/cluster.html.

Examples

# NOT RUN {
  
# }
# 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)
  
# }