#include <thrust/device_vector.h> #include <thrust/sequence.h> #include <thrust/copy.h> #include <thrust/count.h> #include <thrust/remove.h> #include <iostream> #include <iterator> #include <string> // this functor returns true if the argument is odd, and false otherwise template <typename T> struct is_odd : public thrust::unary_function<T,bool> { __host__ __device__ bool operator()(T x) { return x % 2; } }; template <typename Iterator> void print_range(const std::string& name, Iterator first, Iterator last) { typedef typename std::iterator_traits<Iterator>::value_type T; std::cout << name << ": "; thrust::copy(first, last, std::ostream_iterator<T>(std::cout, " ")); std::cout << "\n"; } int main(void) { // input size size_t N = 10; // define some types typedef thrust::device_vector<int> Vector; typedef Vector::iterator Iterator; // allocate storage for array Vector values(N); // initialize array to [0, 1, 2, ... ] thrust::sequence(values.begin(), values.end()); print_range("values", values.begin(), values.end()); // allocate output storage, here we conservatively assume all values will be copied Vector output(values.size()); // copy odd numbers to separate array Iterator output_end = thrust::copy_if(values.begin(), values.end(), output.begin(), is_odd<int>()); print_range("output", output.begin(), output_end); // another approach is to count the number of values that will // be copied, and allocate an array of the right size size_t N_odd = thrust::count_if(values.begin(), values.end(), is_odd<int>()); Vector small_output(N_odd); thrust::copy_if(values.begin(), values.end(), small_output.begin(), is_odd<int>()); print_range("small_output", small_output.begin(), small_output.end()); // we can also compact sequences with the remove functions, which do the opposite of copy Iterator values_end = thrust::remove_if(values.begin(), values.end(), is_odd<int>()); // since the values after values_end are garbage, we'll resize the vector values.resize(values_end - values.begin()); print_range("values", values.begin(), values.end()); return 0; }