Charles, 1. Perhaps this question is better directed at the R-help or R-pacakge-devel mailinglist.
2. It basically means that R itself can only evaluate one R expression at the time. The parallel package circumvents this by starting multiple R-sessions and dividing workload. Compiled code called by R (such as C++ code through RCpp or C-code through base R's interface) can execute multi-threaded code for internal purposes, using e.g. openMP. A limitation is that compiled code cannot call R's C API from multiple threads (in many cases). For example, it is not thread-safe to create R-variables from multiple threads running in C. (R's variable administration is such that the order of (un)making them from compiled code matters). I am not very savvy on Rcpp or XPtr objects, but it appears that Dirk provided answers about that in your SO-question. Best, Mark Op do 12 mei 2016 om 14:46 schreef Charles Determan <cdeterma...@gmail.com>: > R Developers, > > Could someone help explain what it means that R is single threaded? I am > trying to understand what is actually going on inside R when users want to > parallelize code. For example, using mclapply or foreach (with some > backend) somehow allows users to benefit from multiple CPUs. > > Similarly there is the RcppParallel package for RMatrix/RVector objects. > But none of these address the general XPtr objects in Rcpp. Some readers > here may recognize my question on SO ( > > http://stackoverflow.com/questions/37167479/rcpp-parallelize-functions-that-return-xptr > ) > where I was curious about parallel calls to C++/Rcpp functions that return > XPtr objects. I am being a little more persistent here as this limitation > provides a very hard stop on the development on one of my packages that > heavily uses XPtr objects. It's not meant to be a criticism or intended to > be rude, I just want to fully understand. > > I am willing to accept that it may be impossible currently but I want to at > least understand why it is impossible so I can explain to future users why > parallel functionality is not available. Which just echos my original > question, what does it mean that R is single threaded? > > Kind Regards, > Charles > > [[alternative HTML version deleted]] > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
