WISH: Environment varaible to set the default cluster type for parallel:::getClusterOption("type")

[HenrikBengtsson]

(Adopted from an old 2017-09-05 note of mine)

When loaded, have the package set parallel:::defaultClusterOptions$type from (new) environment R_PARALLELLY_CLUSTER_TYPE, if available. This will then allow users to switch the default cluster type used by parallel:::makeCluster().

> parallel:::makeCluster
function (spec, type = getClusterOption("type"), ...) 
{
    switch(type, PSOCK = makePSOCKcluster(spec, ...), FORK = makeForkCluster(spec, 
        ...), SOCK = snow::makeSOCKcluster(spec, ...), MPI = snow::makeMPIcluster(spec, 
        ...), NWS = snow::makeNWScluster(spec, ...), stop("unknown cluster type"))
}
<bytecode: 0x5316668>
<environment: namespace:parallel>

What about snow::makeCluster(), which works the same as parallel::makeCluster() but uses a different default? Contrary to parallel, the parallelly package does not depend/import snow, which means we cannot set ditto for snow. We could add a hook function that does it when / iff the snow package is loaded, but is that good?

Source

• R-devel thread '[parallel-package] feature request: set default cluster type via environment variable', 2016-11-24, https://stat.ethz.ch/pipermail/r-devel/2016-November/073411.html