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#include <thrust/device_vector.h>
#include <thrust/functional.h>
#include <thrust/gather.h>
#include <thrust/iterator/transform_output_iterator.h>
#include <iostream>
#include "include/host_device.h"
struct Functor
{
template <class Tuple>
__host__ __device__ float operator()(const Tuple& tuple) const
{
const float x = thrust::get<0>(tuple);
const float y = thrust::get<1>(tuple);
return x * y * 2.0f / 3.0f;
}
};
int main()
{
float u[4] = {4, 3, 2, 1};
float v[4] = {-1, 1, 1, -1};
int idx[3] = {3, 0, 1};
float w[3] = {0, 0, 0};
thrust::device_vector<float> U(u, u + 4);
thrust::device_vector<float> V(v, v + 4);
thrust::device_vector<int> IDX(idx, idx + 3);
thrust::device_vector<float> W(w, w + 3);
// gather multiple elements and apply a function before writing result in memory
thrust::gather(IDX.begin(),
IDX.end(),
thrust::make_zip_iterator(thrust::make_tuple(U.begin(), V.begin())),
thrust::make_transform_output_iterator(W.begin(), Functor()));
std::cout << "result= [ ";
for (size_t i = 0; i < 3; i++)
{
std::cout << W[i] << " ";
}
std::cout << "] \n";
return 0;
}
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