Functions for computing on a SNOW cluster.
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function or character string naming a function
expression to evaluate
vector to split
character vector of variables to export
environment from which t export variables
additional arguments to pass to standard function
additional argument for
logical; if true shorter arguments are recycled
These are the basic functions for computing on a cluster. All
evaluations on the worker nodes are done using
Currently an error is signaled on the master if any one of the nodes
produces an error. More sophisticated approaches will be considered
in the future.
clusterCall calls a function
fun with identical arguments
... on each node in the cluster
cl and returns a list
of the results.
clusterEvalQ evaluates a literal expression on each cluster node.
It a cluster version of
evalq, and is a convenience function
defined in terms of
fun on the first cluster node with
..., on the second node with
..., and so on. If the length of
seq is greater than the number of nodes in the cluster then
cluster nodes are recycled. A list of the results is returned; the
length of the result list will equal the length of
clusterApplyLB is a load balancing version of
if the length
seq is greater than the number of
n, then the first
n jobs are placed in
order on the
n nodes. When the first job completes, the next
job is placed on the available node; this continues until all jobs
are complete. Using
clusterApplyLB can result in better
cluster utilization than using
increased communication can reduce performance. Furthermore, the
node that executes a particular job is nondeterministic, which can
complicate ensuring reproducibility in simulations.
clusterMap is a multi-argument version of
RECYCLE is true shorter
arguments are recycled; otherwise, the result length is the length of
the shortest argument. Cluster nodes are recycled if the length of
the result is greater than the number of nodes.
clusterExport assigns the values on the master of the variables
list to variables of the same names in the global
environments of each node. The environment on the master from which
variables are exported defaults to the global environment.
seq into one consecutive piece for
each cluster and returns the result as a list with length equal to the
number of cluster nodes. Currently the pieces are chosen to be close
to equal in length. Future releases may attempt to use relative
performance information about nodes to choose split proportional to
For more details see https://stat.uiowa.edu/~luke/R/cluster/cluster.html.
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