how to change device id of thrust::device_vector

Question

is it possible to change the device id of thrust::device vector? I'm thinking to code like this

cudaSetDevice(0);                                //set to device:0
thrust::device_vector<int> a(10);                //define the device vector
a.clear(); thrust::device_vector<int>().swap(a); //deallocate the vector

cudaSetDevice(1);                                //set to device:1
a.resize(10);

is it possible? thanks

Answer 1

I don't know whether this is a correct answer. so please correct me if I'm wrong because i don't whether the test is proper enough. So I decided to do test on vector addition as follows

#include <thrust/device_vector.h>
#include <iostream>

__global__ void
vectorAdd(const int *A, const int *B, int *C, int numElements) {
    int i = blockDim.x * blockIdx.x + threadIdx.x;
    if (i < numElements) C[i] = A[i] + B[i];
};

int main(void)
{
    int numElements = 1024;
    int randacc = 30;

    cudaSetDevice(0);
    thrust::device_vector<int> a(numElements, 1);
    thrust::device_vector<int> b(numElements, 2);
    thrust::device_vector<int> c(numElements);

    int* a_d = thrust::raw_pointer_cast(&a[0]);
    int* b_d = thrust::raw_pointer_cast(&b[0]);
    int* c_d = thrust::raw_pointer_cast(&c[0]);

    int threadsPerBlock = 64;
    int blocksPerGrid =(numElements + threadsPerBlock - 1) / threadsPerBlock;

    vectorAdd<<<blocksPerGrid, threadsPerBlock>>>(a_d, b_d, c_d, numElements);
    cudaError_t err = cudaGetLastError();

    if (err != cudaSuccess) std::cerr << cudaGetErrorString(err) << std::endl;
    std::cout << "random access on dev 0, c = " << c[randacc] << std::endl;

    a.clear(); thrust::device_vector<int>().swap(a); //deallocate the vector
    b.clear(); thrust::device_vector<int>().swap(b); //deallocate the vector
    c.clear(); thrust::device_vector<int>().swap(c); //deallocate the vector

    cudaSetDevice(1);                                //set to device:1
    a.resize(numElements, 1);
    b.resize(numElements, 2);
    c.resize(numElements);

    a_d = thrust::raw_pointer_cast(&a[0]);
    b_d = thrust::raw_pointer_cast(&b[0]);
    c_d = thrust::raw_pointer_cast(&c[0]);

    threadsPerBlock = 64;
    blocksPerGrid =(numElements + threadsPerBlock - 1) / threadsPerBlock;

    vectorAdd<<<blocksPerGrid, threadsPerBlock>>>(a_d, b_d, c_d, numElements);
    err = cudaGetLastError();

    if (err != cudaSuccess) std::cerr << cudaGetErrorString(err) << std::endl;
    std::cout << "random access on dev 1, c = " << c[randacc] << std::endl;

    return 0;
}

and I get result:

random access on dev 0, c = 3

random access on dev 1, c = 3

Note: you need at least 2 GPUs on the same host to test it. i tested on my GTX690