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#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/transform_reduce.h>
#include <thrust/functional.h>
#include <thrust/extrema.h>
#include <thrust/random.h>
// compute minimum and maximum values in a single reduction
// minmax_pair stores the minimum and maximum
// values that have been encountered so far
template <typename T>
struct minmax_pair
{
T min_val;
T max_val;
};
// minmax_unary_op is a functor that takes in a value x and
// returns a minmax_pair whose minimum and maximum values
// are initialized to x.
template <typename T>
struct minmax_unary_op
: public thrust::unary_function< T, minmax_pair<T> >
{
__host__ __device__
minmax_pair<T> operator()(const T& x) const
{
minmax_pair<T> result;
result.min_val = x;
result.max_val = x;
return result;
}
};
// minmax_binary_op is a functor that accepts two minmax_pair
// structs and returns a new minmax_pair whose minimum and
// maximum values are the min() and max() respectively of
// the minimums and maximums of the input pairs
template <typename T>
struct minmax_binary_op
: public thrust::binary_function< minmax_pair<T>, minmax_pair<T>, minmax_pair<T> >
{
__host__ __device__
minmax_pair<T> operator()(const minmax_pair<T>& x, const minmax_pair<T>& y) const
{
minmax_pair<T> result;
result.min_val = thrust::min(x.min_val, y.min_val);
result.max_val = thrust::max(x.max_val, y.max_val);
return result;
}
};
int main(void)
{
// input size
size_t N = 10;
// initialize random number generator
thrust::default_random_engine rng;
thrust::uniform_int_distribution<int> dist(10, 99);
// initialize data on host
thrust::device_vector<int> data(N);
for (size_t i = 0; i < data.size(); i++)
data[i] = dist(rng);
// setup arguments
minmax_unary_op<int> unary_op;
minmax_binary_op<int> binary_op;
// initialize reduction with the first value
minmax_pair<int> init = unary_op(data[0]);
// compute minimum and maximum values
minmax_pair<int> result = thrust::transform_reduce(data.begin(), data.end(), unary_op, init, binary_op);
// print results
std::cout << "[ ";
for(size_t i = 0; i < N; i++)
std::cout << data[i] << " ";
std::cout << "]" << std::endl;
std::cout << "minimum = " << result.min_val << std::endl;
std::cout << "maximum = " << result.max_val << std::endl;
return 0;
}
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