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我想实施 RANSAC。我生成了 60k 点和 500 个平面，我想计算每个平面，它们附近有多少点。然后选择具有最大值的那个。

在我生成向量 ( d_vec) 和平面 ( d_pl) 并将它们传输到 GPU 后，我使用thrust::transform和在其中thrust:count_if计算关闭点的数量。

不幸的是，我收到了这个错误：

1>D:\Projects\cuda\CudaTest\CudaTest>"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\bin\nvcc.exe" -gencode=arch=compute_30,code=\"sm_30,compute_30\" --use-local-env --cl-version 2015 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\x86_amd64" -x cu  -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\include" -I"C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\include"     --keep-dir x64\Release -maxrregcount=0  --machine 64 --compile -cudart static     -DWIN32 -DWIN64 -DNDEBUG -D_CONSOLE -D_MBCS -Xcompiler "/EHsc /W3 /nologo /O2 /FS /Zi  /MD " -o x64\Release\kernel.cu.obj "D:\Projects\cuda\CudaTest\CudaTest\kernel.cu"
1>C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\include\thrust/detail/type_traits/pointer_traits.h(201): error : calling a __host__ function("thrust::detail::vector_base< ::Vec3,  ::thrust::device_malloc_allocator< ::Vec3> > ::begin") from a __device__ function("thrust::cuda_cub::__transform::unary_transform_f< ::thrust::detail::normal_iterator< ::thrust::device_ptr< ::Plane> > ,  ::thrust::detail::normal_iterator< ::thrust::device_ptr<int> > ,  ::thrust::cuda_cub::__transform::no_stencil_tag,  ::plane_functor,  ::thrust::cuda_cub::__transform::always_true_predicate> ::operator ()<long long> ") is not allowed
1>C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v9.0\include\thrust/detail/type_traits/pointer_traits.h(201): error : identifier "thrust::detail::vector_base< ::Vec3,  ::thrust::device_malloc_allocator< ::Vec3> > ::begin" is undefined in device code
1>D:/Projects/cuda/CudaTest/CudaTest/kernel.cu(84): error : calling a __host__ function("thrust::detail::vector_base< ::Vec3,  ::thrust::device_malloc_allocator< ::Vec3> > ::end") from a __device__ function("thrust::cuda_cub::__transform::unary_transform_f< ::thrust::detail::normal_iterator< ::thrust::device_ptr< ::Plane> > ,  ::thrust::detail::normal_iterator< ::thrust::device_ptr<int> > ,  ::thrust::cuda_cub::__transform::no_stencil_tag,  ::plane_functor,  ::thrust::cuda_cub::__transform::always_true_predicate> ::operator ()<long long> ") is not allowed
1>D:/Projects/cuda/CudaTest/CudaTest/kernel.cu(84): error : identifier "thrust::detail::vector_base< ::Vec3,  ::thrust::device_malloc_allocator< ::Vec3> > ::end" is undefined in device code

怎么可能从设备代码调用thrust::count_if？我错了什么？这是完整的代码：

#include <thrust/host_vector.h>
#include <thrust/device_vector.h>
#include <thrust/generate.h>
#include <thrust/sort.h>
#include <thrust/copy.h>
#include <thrust/execution_policy.h>
#include <algorithm>
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <thrust/count.h>
#include <thrust/extrema.h>

struct Vec3 {
    float x;
    float y;
    float z;


    friend std::ostream& operator<<(std::ostream& os, const Vec3& dt);
};

std::ostream& operator<<(std::ostream& os, const Vec3& dt)
{
    os << dt.x << ", " << dt.y << ", " << dt.z;
    return os;
}

struct Plane {

    float a;
    float b;
    float c;
    float d;

    // https://keisan.casio.com/exec/system/1223596129
    static Plane FromPoints(Vec3 A, Vec3 B, Vec3 C) {
        Plane ret;

        ret.a = (B.y - A.y)*(C.z - A.z) - (C.y - A.y)*(B.z - A.z);
        ret.b = (B.z - A.z)*(C.x - A.x) - (C.z - A.z)*(B.x - A.x);
        ret.c = (B.x - A.x)*(C.y - A.y) - (C.x - A.x)*(B.y - A.y);

        ret.d = -(ret.a*A.x + ret.b*A.y + ret.c*A.z);

        return ret;

    }

};

Vec3 generator() {
    return {
        float(rand()) / float(RAND_MAX) * 1000.f,
        float(rand()) / float(RAND_MAX) * 1000.f,
        float(rand()) / float(RAND_MAX) * 1000.f
    };
}

int index_generator() {
    return rand() % 69632;
}

struct plane_distance {

    const Plane pl;

    __device__ plane_distance(const Plane pl) : pl(pl) {}

    __device__ bool operator()(const Vec3& vv) const {
        return fabsf(pl.a*vv.x + pl.b*vv.y + pl.c*vv.z + pl.d) / sqrtf(pl.a*pl.a + pl.b*pl.b + pl.c*pl.c) > 0.128f;
    }

};

struct plane_functor
{
    thrust::device_vector<Vec3>& d_vec;

    plane_functor(thrust::device_vector<Vec3>& d_vec) : d_vec(d_vec) {}

    __device__ int operator()(const Plane& pl) const {

        return thrust::count_if(thrust::device, d_vec.begin(), d_vec.end(), plane_distance(pl));

    }
};

int main(void)
{


    // Generate random points for testing

    std::cout << "Generating..." << std::endl;

    // generate random vectors serially
    thrust::host_vector<Vec3> h_vec(65536);
    std::generate(h_vec.begin(), h_vec.end(), generator);

    // Generate random planes
    thrust::host_vector<Plane> h_pl(512);
    std::generate(h_pl.begin(), h_pl.end(), [&h_vec]() {

        return Plane::FromPoints(
            h_vec[index_generator()],
            h_vec[index_generator()],
            h_vec[index_generator()]
        );

    });

    std::cout << "Transfer" << std::endl;

    // transfer data to the device
    thrust::device_vector<Vec3> d_vec = h_vec;
    thrust::device_vector<Plane> d_pl = h_pl;
    thrust::device_vector<int> counts(512);

    std::cout << "Searching" << std::endl;

    thrust::transform(thrust::device, d_pl.begin(), d_pl.end(), counts.begin(), plane_functor(d_vec));

    auto result = thrust::max_element(thrust::device, counts.begin(), counts.end());

    std::cout << "Press any key to exit" << std::endl;
    std::cin.get();

    return 0;
}
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1 回答 1

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正如评论中所建议的，device_vector在设备代码中访问是非法的。在撰写本文时，它们是（尽管有它们的名字）所有可用的 Thrust 版本中的主机端抽象。您会收到错误，因为您的仿函数正在设备代码中调用 device_vector 的复制构造，这需要构造新容器并且将调用内存分配并且无法编译。

您应该能够使用原始设备指针来使其工作，例如：

struct plane_functor
{
    Vec3* d_vec0;
    Vec3* d_vec1;

    __host__ __device__ plane_functor(Vec3* d_vec0, Vec3* d_vec1) : d_vec0(d_vec0), d_vec1(d_vec1) {}

    __device__ int operator()(const Plane& pl) const {

        return thrust::count_if(thrust::device, d_vec0, d_vec1, plane_distance(pl));

    }
};

// ....

Vec3* d_vec0 = thrust::raw_pointer_cast(d_vec.data());
Vec3* d_vec1 = d_vec0 + (d_vec.end() - d_vec.begin());
thrust::transform(d_pl.begin(), d_pl.end(), counts.begin(), plane_functor( d_vec0, d_vec1 ) );

请注意，虽然它为我编译，但我无法运行您的代码，因为当我尝试运行它时主机端初始化 lambda 会爆炸。还要密切注意您对标签和基于策略的执行的混合。由于thrust::transform迭代device_vector器和thrust::device.

于 2018-05-07T07:01:07.447 回答