/** * @title Summing a Vector in Parallel with RcppParallel * @author JJ Allaire * @license GPL (>= 2) */ #include #include // [[Rcpp::depends(RcppParallel)]] using namespace RcppParallel; using namespace Rcpp; struct Sum : public Worker { // source vector const RVector input; // accumulated value double value; // constructors Sum(const NumericVector input) : input(input), value(0) {} Sum(const Sum& sum, Split) : input(sum.input), value(0) {} // accumulate just the element of the range I have been asked to void operator()(std::size_t begin, std::size_t end) { value += std::accumulate(input.begin() + begin, input.begin() + end, 0.0); } // join my value with that of another Sum void join(const Sum& rhs) { value += rhs.value; } }; // [[Rcpp::export]] double parallelVectorSum(NumericVector x) { // declare the SumBody instance Sum sum(x); // call parallel_reduce to start the work parallelReduce(0, x.length(), sum); // return the computed sum return sum.value; } // [[Rcpp::export]] double vectorSum(NumericVector x) { return std::accumulate(x.begin(), x.end(), 0.0); }