A thrust problem: How can I copy a host_vector to device_vector with a customized permutation order?

I have an array in host, and I want to transfer it to device with a different order.

I have tried this toy code complied with nvc++ test.cpp -stdpar

$ cat test.cpp
#include <iostream>
#include <thrust/iterator/permutation_iterator.h>
#include <thrust/copy.h>
#include <thrust/sequence.h>
#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include <array>

using Real = float;

int main(int argc, char* argv[]) {

        std::array<std::size_t,6> idx{0,1,2,3,5,4};


        thrust::host_vector<Real> hvec(6);

        thrust::sequence(hvec.begin(),hvec.end());

        typedef thrust::host_vector<Real>::iterator EleItor;
        typedef std::array<std::size_t,6>::iterator IdxItor;

        thrust::permutation_iterator<EleItor,IdxItor> itor(hvec.begin(),idx.begin());

        thrust::device_vector<Real> test;
        thrust::copy(itor,itor+6,test);  // error
        thrust::copy(itor,itor+6,std::ostream_iterator<Real>(std::cout," ");  

}

The problem is that thrust::copy does not allow copy from host to device, how can I bypass this restriction?

>Solution :

According to the documentation is is possible to use thrust::copy to copy from host to device, but you need to pass the device iterator:

//-----------------------------vvvvvvvv--
thrust::copy(itor, itor+6, test.begin());

Note that before that you need to allocate memory for the device vector.
Fortunately the thrust::device_vector has a ctor supports passing a size which will allocate the required memory.
You can use something like:

thrust::device_vector<Real> test(host_vector.size());