I am trying to parallelize a double for loop with RcppArmadillo, but I am having trouble with the kind of arithmetic operations that are available to RMatrix and RVector. I looked at the header file available on github, and I don't see anything there, so I guess I am looking in the wrong place. This is my worker, and I commented where I am trying to do arithmetic operations between two RMatrix objects.
#include <RcppParallel.h>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <Rmath.h>
#include <RcppArmadillo.h>
using namespace RcppParallel;
struct ClosestMean : public Worker {
// Input data and means matrix
const RMatrix<double> input_data;
const RMatrix<double> means;
// Output labels
RVector<int> predicted_labels;
// constructor
ClosestMean(const Rcpp::NumericMatrix input_data, const Rcpp::NumericMatrix means, Rcpp::IntegerVector predicted_labels)
: input_data(input_data), means(means), predicted_labels(predicted_labels) {}
// function call operator for the specified range (begin/end)
void operator () (std::size_t begin, std::size_t end){
for (unsigned int i = begin; i < end; i++){
// Check for User Interrupts
Rcpp::checkUserInterrupt();
// Get the label corresponding to the cluster mean
// for which the point is closest to
RMatrix<double>::Row point = input_data.row(i);
int label_min = -1;
double dist;
double min_dist = INFINITY;
for (unsigned int j = 0; j < means.nrow(); j++){
RMatrix<double>::Row mean = means.row(j);
dist = sqrt(Rcpp::sum((mean - point)^2)); // This is where the operation is failing
if (dist < min_dist){
min_dist = dist;
label_min = j;
}
}
predicted_labels[i] = label_min;
}
}
};
Thanks for any advice.