Fast way to call an R function from C++?
Hello Kevin and I?aki, Thanks for your quick responses. I sincerely appreciate them! I can see how complicated it is to interact with R in C. I?aki's suggestion is very helpful, I saw there is a lot of performance gain by turning the flag on, but sadly the best performance it can offer still cannot beat R itself. It is interesting to see that C++ is worse than R in this special case despite there is a common belief that C++ code is the fast one... Anyway, thanks again for your suggestions and reference! Best, Jiefei
On Tue, Jun 18, 2019 at 2:39 PM I?aki Ucar <iucar at fedoraproject.org> wrote:
For reference, your benchmark using UNWIND_PROTECT:
system.time(test(testFunc, evn$x))
user system elapsed 0.331 0.000 0.331
system.time(test(C_test1, testFunc, evn$x))
user system elapsed 2.029 0.000 2.036
system.time(test(C_test2, expr, evn))
user system elapsed 2.307 0.000 2.313
system.time(test(C_test3, testFunc, evn$x))
user system elapsed 2.131 0.000 2.138 I?aki On Tue, 18 Jun 2019 at 20:35, I?aki Ucar <iucar at fedoraproject.org> wrote:
On Tue, 18 Jun 2019 at 19:41, King Jiefei <szwjf08 at gmail.com> wrote:
[...] It is clear to see that calling an R function in R is the fast one, it
is
about 5X faster than ` R_forceAndCall ` and ` Rf_eval`. the latter two functions have a similar performance and using Rcpp is the worst one.
Is it
expected? Why is calling an R function from C++ much slower than
calling
the function from R? Is there any faster way to do the function call
in C++?
Yes, there is: enable fast evaluation by setting -DRCPP_USE_UNWIND_PROTECT, or alternatively, use // [[Rcpp::plugins(unwindProtect)]] I?aki
-- I?aki ?car