当通过Rcpp调用boost :: threadpool时，RStudio挂起

Question

I'm having a problem calling a local library through Rcpp with R Studio Server. It's a bit perplexing, since I have no issues when I call it from R at the command line.

I've written an analytics library which uses boost's threadpool functionality for running multiple threads. I've stripped everything down to the bare essentials, the minimum code which will cause the problem -- this code just starts the threads in the threadpool, then exits them:

#include <Rcpp.h>

#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/thread.hpp>

RcppExport SEXP test_thread()
{
BEGIN_RCPP
    double retdbl = 10.4;

    boost::shared_ptr<boost::asio::io_service::work> threadpool_work;
    boost::asio::io_service threadpool_io_service;
    boost::thread_group threadpool_threads;

    threadpool_work.reset(  new         
        boost::asio::io_service::work(threadpool_io_service)  );
    for (int i = 0; i < 6; ++i) {
        threadpool_threads.create_thread(
            boost::bind(&boost::asio::io_service::run, &threadpool_io_service));
    }

    threadpool_io_service.stop();
    threadpool_work.reset();
    threadpool_threads.join_all();

    return(  Rcpp::wrap(retdbl)  );
END_RCPP
}

When I run from command-line R, there's no problem. I get the double returned. However, when I run through R Studio Server, it either hangs endlessly, or it crashes when it gets to the create_thread statement.

My version info is:

• R: R version 3.1.1 (2014-07-10) -- "Sock it to Me"
• R Studio: 0.99.489
• Linux: Linux Debian-Jessie 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt11-1+deb8u6 (2015-11-09) x86_64 GNU/Linux
• boost: 1.55

Answer 1

That may just be your cost of running inside RStudio with threaded code . RStudio itself is using Boost for this, and also talking to R -- so it seems that two event queues are getting mixed up. I think short of talking to them there is little you can do.

I really do like littler for running bigger jobs as scripts on the command-line. It has been part of Debian since 2006 too as is just an apt-get away for you.

Edit: As an Rcpp aside you can write your function more compactly as

// [[Rcpp::export]]
double test_thread() {
    double retdbl = 10.4;

    boost::shared_ptr<boost::asio::io_service::work> threadpool_work;
    boost::asio::io_service threadpool_io_service;
    boost::thread_group threadpool_threads;

    threadpool_work.reset(  new         
        boost::asio::io_service::work(threadpool_io_service)  );
    for (int i = 0; i < 6; ++i) {
        threadpool_threads.create_thread(
            boost::bind(&boost::asio::io_service::run, &threadpool_io_service));
    }

    threadpool_io_service.stop();
    threadpool_work.reset();
    threadpool_threads.join_all();

    return(retdbl);
}

See the vignette Rcpp Attributes for details; you probably want to call compileAttributes() in the package directory; RStudio will do it to your source package.