# availableWorkers

0th

Percentile

##### Get set of available workers

Get set of available workers

Keywords
internal
##### Usage
availableWorkers(
methods = getOption("future.availableWorkers.methods", c("mc.cores",
"_R_CHECK_LIMIT_CORES_", "PBS", "SGE", "Slurm", "custom", "system", "fallback")),
na.rm = TRUE,
default = "localhost",
which = c("auto", "min", "max", "all")
)
##### Arguments
methods

A character vector specifying how to infer the number of available cores.

na.rm

If TRUE, only non-missing settings are considered/returned.

default

The default set of workers.

which

A character specifying which set / sets to return. If "auto", the first non-empty set found. If "min", the minimum value is returned. If "max", the maximum value is returned (be careful!) If "all", all values are returned.

##### Details

The default set of workers for each method is rep("localhost", times = availableCores(method)), which means that each will at least use as many parallel workers on the current machine that availableCores() allows for that method.

In addition, the following settings ("methods") are also acknowledged:

• "PBS" - Query TORQUE/PBS environment variable PBS_NODEFILE. If this is set and specifies an existing file, then the set of workers is read from that file, where one worker (node) is given per line. An example of a job submission that results in this is qsub -l nodes = 4:ppn = 2, which requests four nodes each with two cores.

• "SGE" - Query Sun/Oracle Grid Engine (SGE) environment variable PE_HOSTFILE. An example of a job submission that results in this is qsub -pe mpi 8 (or qsub -pe ompi 8), which requests eight cores on a any number of machines.

• "custom" - If option future.availableWorkers.custom is set and a function, then this function will be called (without arguments) and it's value will be coerced to a character vector, which will be interpreted as hostnames of available workers.

##### Value

Return a character vector of workers, which typically consists of names of machines / compute nodes, but may also be IP numbers.

To get the number of available workers on the current machine, see availableCores().