CUDA-Thrust(2)--野指针转换

1.野指针：

　　前两篇博文定义的向量都是在device_vector和host_vector向量空间，如果我们定义一个

像int* raw_ptr的野指针，怎样实现数据间的传递呢？Thrust提供给我们一些函数帮助我们解决

这样的问题。thrust::raw_pointer_cast和thrust::device_ptr<int> dev_ptr(raw_ptr)。

2.代码：

　　接下来的例子就是为展示，野指针在device_vector在空间中的操作：

#include "cuda_runtime.h"
#include "device_launch_parameters.h"

#include <stdio.h>

#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include <thrust/copy.h>
#include <thrust/fill.h>
#include <thrust/sequence.h>
#include <iostream>


int main(void) {

    int N = 10;

    //define H on host
    thrust::host_vector<int>H(N);

    //initialize H
    thrust::sequence(H.begin(), H.end(), 0);

    //show the sequence H
    std::cout << "show the original H" << std::endl;
    for (int i = 0; i < H.size(); ++i)
        std::cout << "H[" << i << "]=" << H[i] << std::endl;

    // raw pointer to device memory
    int * raw_ptr;
    cudaMalloc((void **)&raw_ptr, N * sizeof(int));

    // wrap raw pointer with a device_ptr 
    thrust::device_ptr<int> dev_ptr(raw_ptr);

    //copy the elements from host_vector to device_vector
    thrust::copy(H.begin(), H.end(), dev_ptr);
    
    //extract raw pointer from device_ptr
    raw_ptr = thrust::raw_pointer_cast(dev_ptr);

    int *test = new int[N];
    cudaMemcpy(test, raw_ptr, N * sizeof(int), cudaMemcpyDeviceToHost);
    
    //show the sequence test
    std::cout << "show the original test" << std::endl;
    for (int i = 0; i < H.size(); ++i)
        std::cout << "test[" << i << "]=" << test[i] << std::endl;

    delete(test);
    cudaFree(raw_ptr);
    return 0;
}