On Wed, Dec 8, 2010 at 3:02 PM, Dirk Eddelbuettel <[email protected]> wrote:
>
> On 8 December 2010 at 13:41, Andrew Redd wrote:
> | I have an MCMC chain that runs entirely in c++ with Rcpp. It sometimes runs
> | for a vary long time and I want to interrupt it. Is there an efficient easy
> | way to include catching an interupt signal and either aborting or returning
> | results to that point? This might be understood well, if so I apologize.
>
> Great question.
>
> Here is a simple example that uses a standard C interrupt handler to set a
> standard C++ exception to abort:
>
> ----------------------------------------------------------------
>
> #include <csignal>
> #include <Rcpp.h>
>
> void intHandler(int dummy=0) {
> std::cerr << "In intHandler" << std::endl;
> throw std::runtime_error("Interception caught");
> }
Gee, I wouldn't have pictured you as an American football fan. I
think you meant "interrupt caught".
> RcppExport SEXP foo(void) {
>
> try {
>
> signal(SIGINT, intHandler);
> signal(SIGKILL, intHandler);
>
> while (true) {
> sleep(1); // not doing much
> }
> return R_NilValue;
>
> } catch(std::exception &ex) {
> std::cerr << "In catch of std::exeception" << std::endl;
> // here you insert some clenup
> forward_exception_to_r(ex);
>
> } catch(...) {
> ::Rf_error("c++ exception (unknown reason)");
> }
>
> return R_NilValue;
> }
>
> ----------------------------------------------------------------
>
> which I then quickly turned into a shared object, load and ran at the
> command-line [1]
>
> e...@max:/tmp/andrew$ PKG_CPPFLAGS=`r -e'Rcpp:::CxxFlags()'` PKG_LIBS=`r
> -e'Rcpp:::LdFlags()'` R CMD SHLIB int2throw.cpp
> ccache g++ -I/usr/share/R/include
> -I/usr/local/lib/R/site-library/Rcpp/include -fpic -g -O3 -Wall -pipe
> -pedantic -Wno-variadic-macros -c int2throw.cpp -o int2throw.o
> g++ -shared -o int2throw.so int2throw.o
> -L/usr/local/lib/R/site-library/Rcpp/lib -lRcpp
> -Wl,-rpath,/usr/local/lib/R/site-library/Rcpp/lib -L/usr/lib64/R/lib -lR
> e...@max:/tmp/andrew$ r -e'dyn.load("int2throw.so"); .Call("foo")'
> ^CIn intHandler
> In catch of std::exeception
> Error in cpp_exception(message = "Interception caught", class =
> "std::runtime_error") :
> Interception caught
> Execution halted
> e...@max:/tmp/andrew$
> e...@max:/tmp/andrew$
>
>
> After lauching it from the one-line littler (r) expression, I pressed Ctrl-C
> which then got us into the interrupt which threw the exception which lead to
> the end.
>
> In Rscript it looks a little more orderly on the unwind:
>
> e...@max:/tmp/andrew$ Rscript -e 'dyn.load("int2throw.so"); .Call("foo")'
> C-c C-cIn intHandler
> In catch of std::exeception
> Error in cpp_exception(message = "Interception caught", class =
> "std::runtime_error") :
> Interception caught
> Calls: .Call -> cpp_exception
> Execution halted
> e...@max:/tmp/andrew$
>
>
> Hope this helps, Dirk
>
>
> [1] Not sure why I didn't use inline today...
>
>
> --
> Dirk Eddelbuettel | [email protected] | http://dirk.eddelbuettel.com
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