raster (version 1.9-44)

cluster: Use a multi-core cluster

Description

beginCluster creates, and endCluster deletes a 'snow' cluster object. This object can be used for multi-core computing with those 'raster' functions that support it. beginCluster determines the number of nodes (cores) that are available and uses all of them (unless the argument n is used). NOTE: beginCluster may fail when the package 'nws' is installed. You can fix that by removing the 'nws' package, or by setting the cluster type manually, e.g. beginCluster(type="SOCK") endCluster closes the cluster and removes the object. The use of the cluster is automatic in these functions" predict, projectRaster, resample and in extract when using polygons. clusterR is a flexible interface for using cluster with other functions. This function only works with functions from the raster package that return Raster* objects that operate on a cell by cell basis and return an object with the same number of cells as the input raster object(s). Among other functions, it does _not_ work with mrege, crop, mosaic, (dis)aggregate, resample, projectRaster, focal, distance, direction.

Usage

beginCluster(n, type, nice, exclude)
endCluster()
clusterR(x, fun, args=NULL, filename='', cl=NULL, m=2, ...)

Arguments

n

Integer. The number of nodes to be used (optional)

type

Character. The cluster type to be used (optional). E.g. "SOCK", see the snow package for details

nice

Integer. To set the prioirty for the workers, between -20 and 20 (UNIX like platforms only)

exclude

Character. Packages to exclude from loading on the nodes (because they may fail there) but are required/loaded on the master

x

Raster* object

fun

function

args

arguments for the function (excluding x, which should always be the first argument

filename

character. Output filename (optional)

cl

cluster object (do not use it if beginCluster() has been called

m

tuning parameter to determine how many blocks should be used. The number is rounded and multiplied with the number of nodes.

...

additional arguments for writing Raster objects to disk

Value

• None. The side effect is to create or delete a cluster object.

Examples

#beginCluster()
beginCluster(type="SOCK")

r <- raster()
r[] <- 1:ncell(r)

x <- clusterR(r, sqrt, verbose=T)

f1 <- function(x) calc(x, sqrt)
y <- clusterR(r, f1)

s <- stack(r, r*2, r*3)
f2 <- function(x) calc(x, range)
z <- clusterR(s, f2)

pts <- matrix(c(0,0, 45,45), ncol=2, byrow=T)
d <- clusterR(r, distanceFromPoints, args=list(xy=pts))

endCluster()