Change default for max.load

[krlmlr]

In makeClusterFunctionsMulticore, the argument max.load defaults to ncpus - 1. I think this should rather be detectCores() - 1 or detectCores() (not even related to the mc.cores option). The load should be limited by the available physical resources, not by what we allow the current process to use.

Example: Assume four cores, two of which are busy. I want to limit a computation to the two remaining cores and therefore say makeClusterFunctionsMulticore(2), to the effect that no workers are allowed to start because the load (2) is clearly larger than ncpus - 1.

On that note, what is the practical difference between ncpus and max.jobs?
#62 is slightly related.

[mllg]

Yep, that is a much better default. Note that we are well aware that the our choices are pretty defensive (as we want to avoid automatic over-utilization). We kind of expect the user to choose sane and efficient defaults.