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#include <thrust/device_vector.h>
#include <thrust/iterator/permutation_iterator.h>
#include <thrust/reduce.h>
#include <iostream>
// this example fuses a gather operation with a reduction for
// greater efficiency than separate gather() and reduce() calls
int main()
{
// gather locations
thrust::device_vector<int> map(4);
map[0] = 3;
map[1] = 1;
map[2] = 0;
map[3] = 5;
// array to gather from
thrust::device_vector<int> source(6);
source[0] = 10;
source[1] = 20;
source[2] = 30;
source[3] = 40;
source[4] = 50;
source[5] = 60;
// fuse gather with reduction:
// sum = source[map[0]] + source[map[1]] + ...
int sum = thrust::reduce(thrust::make_permutation_iterator(source.begin(), map.begin()),
thrust::make_permutation_iterator(source.begin(), map.end()));
// print sum
std::cout << "sum is " << sum << std::endl;
return 0;
}
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