I posted the following to SO earlier this morning and it was suggested that I repost this question to the rcpp-devel list for exposure. For reference, the original posting is at http://stackoverflow.com/questions/27089888/rcppparallel-example-crashing-r.
I have been trying to parallelize one of my Rcpp routines. In doing so I have been trying to follow the [Parallel Distance Calculation]( http://gallery.rcpp.org/articles/parallel-distance-matrix/) example from jjalaire. Unfortunately, once I got everything coded up and started to play around, my R session would crash. Sometimes after the first execution, sometimes after the third. To be honest, it was a crap shoot as to when R would crash when I ran the routine. So, I have paired down my code to a small reproducible example to play with. ***Rcpp File (mytest.cpp)*** ------------------------------------------------------------------------------------------------------------ #include <Rcpp.h> // [[Rcpp::depends(RcppParallel)]] #include <RcppParallel.h> using namespace std; using namespace Rcpp; using namespace RcppParallel; struct MyThing : public Worker { RVector<double> _pc; RVector<double> _pcsd; MyThing(Rcpp::NumericVector _pc, Rcpp::NumericVector _pcsd) : _pc(_pc), _pcsd(_pcsd){} void operator()(std::size_t begin, std::size_t end) { for(int j = begin; j <= end; j++) { _pc[j] = 1; // _pcsd[j] = 1; } } }; // [[Rcpp::export]] void calculateMyThingParallel() { NumericVector _pc(100); NumericVector _pcsd(100); MyThing mt(_pc, _pcsd); parallelFor(0, 100, mt); } ------------------------------------------------------------------------------------------------------------ ***R Compilation and Execution Script (mytest.R)*** ------------------------------------------------------------------------------------------------------------ library(Rcpp) library(inline) sourceCpp('mytest.cpp') testmything = function() { calculateMyThingParallel() } if(TRUE) { for(i in 1:20) { testmything() } } ------------------------------------------------------------------------------------------------------------ The error seems to be directly related to my setting of the _pc and _pcsd variables in the `operator()` method. If I take those out things dramatically improve. Based on the Parallel Distance Calculation example, I am not sure what it is that I have done wrong here. I was under the impression that RVector<type> was thread safe. Although that is my impression, I know this is an issue with threads somehow. Can anybody help me to understand why the above code randomly crashes my R sessions? For information I am running the following: - Windows 7 - R: 3.1.2 - Rtools: 3.1 - Rcpp: 0.11.3 - inline: 0.3.13 - RStudio: 0.99.62
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