Hello Justace, It seems that you should write down j < end rather than j <= end.
Best, Yixuan 2014-11-23 21:10 GMT-05:00 Justace Clutter <justa...@gmail.com>: > 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 > > > _______________________________________________ > Rcpp-devel mailing list > Rcpp-devel@lists.r-forge.r-project.org > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > -- Yixuan Qiu <yixuan....@cos.name> Department of Statistics, Purdue University
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