https://github.com/cran/snowfall
Revision c007f9972e17df4f554e4359570e909c6824ca9d authored by Jochen Knaus on 19 June 2008, 00:00:00 UTC, committed by Gabor Csardi on 19 June 2008, 00:00:00 UTC
0 parent
Tip revision: c007f9972e17df4f554e4359570e909c6824ca9d authored by Jochen Knaus on 19 June 2008, 00:00:00 UTC
version 1.51
version 1.51
Tip revision: c007f99
snowfall-b-init.Rd
\name{snowfall-init}
\alias{sfInit}
\alias{sfStop}
\alias{sfParallel}
\alias{sfCpus}
\alias{sfNodes}
\alias{sfGetCluster}
\alias{sfSession}
\alias{sfSetMaxCPUs}
\title{Initialisation of cluster usage}
\usage{
sfInit( parallel=NULL, cpus=NULL, nostart=FALSE )
sfStop( nostop=FALSE )
sfParallel()
sfCpus()
sfNodes()
sfGetCluster()
sfSession()
sfSetMaxCPUs( number=32 )
}
\arguments{
\item{parallel}{Logical determinating parallel or sequential
execution. If not set values from commandline are taken.}
\item{cpus}{Numerical amount of CPUs requested for the cluster. If
not set, values from the commandline are taken.}
\item{nostart}{Logical determinating if the basic cluster setup should
be skipped. Needed for nested use of \pkg{snowfall} and usage in
packages.}
\item{nostop}{Same as noStart for ending.}
\item{number}{Amount of maximum CPUs useable.}
}
\description{
Initialisation and organisation code to use \pkg{snowfall}.
}
\details{
\code{sfInit} initialisise the usage of the \pkg{snowfall} functions
and - if running in parallel mode - setup the cluster and
\pkg{snow}. If using
\code{sfCluster} management tool, call this without arguments. If
\code{sfInit} is called with arguments, these overwrite
\code{sfCluster} settings. If running parallel, \code{sfInit}
set up the
cluster by calling \code{makeCluster} from \pkg{snow}. If using with
\code{sfCluster}, the initialisation also contains management of
lockfiles. If this function is called more than once and current
cluster is yet running, \code{sfStop} is called automatically.
Note that you MUST call \code{sfInit} before using any other function
from \pkg{snowfall}, with the only exception \code{sfSetMaxCPUs}.
If you use \pkg{snowfall} in a package argument \code{nostart} is very
handy if mainprogram uses \pkg{snowfall} as well. If set, cluster
setup will be skipped and both parts (package and main program) use
the same cluster.
If you call \code{sfInit} more than one time in a program without
explicit calling \code{sfStop}, stopping of the cluster will be
executed automatically. If your R-environment does not cover required
libraries, \code{sfInit} automatically switches to sequential mode
(with a warning). Required libraries for parallel usage are \pkg{snow}
and \pkg{Rmpi}.
Note there is limit on CPUs used in one program (which can be
configured on package installation). The current limit are 32 CPUs. If
you need a higher amount of CPUs, call \code{sfSetMaxCPUs}
\emph{before} the first call to \code{sfInit}. The limit is set to
prevent inadvertently request by single users affecting the cluster as
a whole.
\code{sfStop} stop cluster. If running in parallel mode, the LAM/MPI
cluster is shut down.
\code{sfParallel}, \code{sfCpus} and \code{sfSession} grant access to
the internal state of the currently used cluster.
All three can be configured via commandline and especially with
\code{sfCluster} as well, but given
arguments in \code{sfInit} always overwrite values on commandline.
The commandline options are \option{--parallel} (empty option. If missing,
sequential mode is forced), \option{--cpus=X} (for nodes, where X is a
numerical value) and \option{--session=X} (with X a string).
\code{sfParallel} returns a
logical if program is running in parallel/cluster-mode or sequential
on a single processor.
\code{sfCpus} returns the size of the cluster in CPUs
(equals the CPUs which are useable). In sequential mode \code{sfCpus}
returns one. \code{sfNodes} is a deprecated similar to \code{sfCpus}.
\code{sfSession} returns a string with the
session-identification. It is mainly important if used with the
\code{sfCluster} tool.
\code{sfGetCluster} gets the \pkg{snow}-cluster handler. Use for
direct calling of \pkg{snow} functions.
\code{sfSetMaxCPUs} enables to set a higher maximum CPU-count for this
program. If you need higher limits, call \code{sfSetMaxCPUs} before
\code{sfInit} with the new maximum amount.
}
\keyword{package}
\seealso{
See snow documentation for details on commands:
\code{\link[snow:snow-package]{snow}}
}
\examples{
\dontrun{
# Run program in plain sequential mode.
sfInit( parallel=FALSE )
stopifnot( sfParallel() == FALSE )
sfStop()
# Run in parallel mode overwriting probably given values on
# commandline. Hooks in running LAM cluster, if none is running,
# snow is spawning one on localhost.
sfInit( parallel=TRUE, nodes=10 )
stopifnot( sfCpus() == 10 )
stopifnot( sfParallel() == TRUE )
sfStop()
# Run in sfCluster-mode: settings are taken from commandline.
sfInit()
# Session-ID from sfCluster (or XXXXXXXX as default)
session <- sfSession()
# Calling a snow function: cluster handler needed.
parLapply( sfGetCluster(), 1:10, exp )
# Same using snowfall wrapper, no handler needed.
sfLapply( 1:10, exp )
sfStop()
}
}
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