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#include <thrust/copy.h>
#include <thrust/count.h>
#include <thrust/device_vector.h>
#include <thrust/remove.h>
#include <thrust/sequence.h>
#include <iostream>
#include <iterator>
#include <string>
#include "include/host_device.h"
// 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()
{
// 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;
}
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