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/**
*
* This file contains example code showcasing how RcppParallel
* can be used. In this file, we define and export a function called
* 'parallelVectorSum()', which computes the sum of a numeric vector
* in parallel.
*
* Please see https://rcppcore.github.io/RcppParallel/ for more
* details on how to use RcppParallel in an R package, and the
* Rcpp gallery at http://gallery.rcpp.org/ for more examples.
*
*/
// [[Rcpp::depends(RcppParallel)]]
#include <Rcpp.h>
#include <RcppParallel.h>
using namespace Rcpp;
using namespace RcppParallel;
struct Sum : public Worker
{
// source vector
const RVector<double> 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've 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;
}
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