Cluster: Use a multi-core (snow) cluster

Description

Create or delete a 'snow' cluster object. This object provides _experimental_ support for multi-core computing with a few 'raster' functions that support it. beginCluster creates the cluster object. It 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 by functions is automatic, but has only been implemented in a few functions.

Usage

beginCluster(n, type, nice)
endCluster()

Arguments

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)

Value

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

Details

Functions that are 'cluster-enabled' are: projectRaster, resample, distance, extract (when using polygons). If you want to write your own cluster-enabled functions see getCluster, returnCluster, and the vignette about writing functions

Examples

Run this code

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

r <- raster(ncol=36, nrow=18)
r[] <- NA
r[500] <- 1
dist <- distance(r) 

endCluster()