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#include <thrust/copy.h>
#include <thrust/device_vector.h>
#include <thrust/functional.h>
#include <thrust/iterator/counting_iterator.h>
#include <iostream>
#include <iterator>
int main()
{
// this example computes indices for all the nonzero values in a sequence
// sequence of zero and nonzero values
thrust::device_vector<int> stencil(8);
stencil[0] = 0;
stencil[1] = 1;
stencil[2] = 1;
stencil[3] = 0;
stencil[4] = 0;
stencil[5] = 1;
stencil[6] = 0;
stencil[7] = 1;
// storage for the nonzero indices
thrust::device_vector<int> indices(8);
// counting iterators define a sequence [0, 8)
thrust::counting_iterator<int> first(0);
thrust::counting_iterator<int> last = first + 8;
// compute indices of nonzero elements
typedef thrust::device_vector<int>::iterator IndexIterator;
IndexIterator indices_end = thrust::copy_if(first, last, stencil.begin(), indices.begin(), thrust::identity<int>());
// indices now contains [1,2,5,7]
// print result
std::cout << "found " << (indices_end - indices.begin()) << " nonzero values at indices:\n";
thrust::copy(indices.begin(), indices_end, std::ostream_iterator<int>(std::cout, "\n"));
return 0;
}
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