R: Starting and Stopping SNOW Clusters

snow-startstop {snow} | R Documentation

## 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)
    makeNWScluster(names, ..., 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"`, `"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 option`outfile` 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.

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

### Examples

      ## 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)

[Package snow version 0.4-2 Index]