I would say that was it... Thanks for catching that. Sometimes the smallest thing can get you. I have updated the SO question with the answer.
Now that I got this working I am seeing great speed improvements: b1 = R native code b2 = Rcpp non parallel b3 = Rcpp parallel test replications elapsed relative user.self sys.self user.child sys.child 1 b1() 10 1760.65 78.776 1753.76 0.56 NA NA 2 b2() 10 128.78 5.762 128.38 0.05 NA NA 3 b3() 10 22.35 1.000 170.68 0.06 NA NA On Sun, Nov 23, 2014 at 9:15 PM, Yixuan Qiu <yixuan....@cos.name> wrote: > 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 >
_______________________________________________ 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
