c++ - OpenCL的部分封装导致段错误，包括代码示例

Question

这让我很困惑。两组代码在逻辑上应该是相同的，一组只在 GPU 上崩溃，而两套在 CPU 上运行良好。这是测试代码:

#include <iostream>
#include <CL/cl.hpp>

class Device
{
public:
    cl::Platform platform_;
    cl::Device device_;
    cl::Context context_;
    cl::CommandQueue queue_;

    Device( void ) : platform_()
                   , device_()
                   , context_()
                   , queue_() {}

    Device(int32_t platform, int32_t device) : platform_()
                                             , device_()
                                             , context_()
                                             , queue_()
    {
        std::vector<cl::Platform> platforms;
        cl::Platform::get(&platforms);
        platform_ = platforms[platform];

        std::vector<cl::Device> devices;
        platform_.getDevices(CL_DEVICE_TYPE_GPU, &devices);
        device_ = devices[device];

        cl_context_properties properties[3] = {
            CL_CONTEXT_PLATFORM,
            (cl_context_properties)(platform_)(),
            0
        };

        cl_int clErr = CL_SUCCESS;
        context_ = cl::Context(device_, properties, NULL, NULL, &clErr);
        queue_ = cl::CommandQueue(context_,device_,0,&clErr);
    }
};

int main()
{
    Device device(0,0);

    cl::Program::Sources source;
    std::string src =
    "__kernel void Pointless(uint total, __global uint *data)"\
    "{"\
    "   uint perStream=total/get_global_size(0);"\
    "   __global uint *dest=data+get_global_id(0)*perStream;"\
    "   for(uint i=0;i<perStream;i++)"\
    "       dest[i] = 1;"\
    "}";

    source.push_back({src.c_str(),src.length()});

    cl_int clErr = CL_SUCCESS;
    cl::Program program = cl::Program(device.context_,source,&clErr);
    if (clErr != CL_SUCCESS)
    {
        std::cerr << "Failed to create program: " << clErr << std::endl;
        return 1;
    }

    clErr = program.build({device.device_});
    if(clErr != CL_SUCCESS)
    {
        std::cerr << "Failed to build program: " << clErr << std::endl;
        std::cerr << program.getBuildInfo<CL_PROGRAM_BUILD_LOG>(device.device_) << std::endl;
        return 1;
    }

    uint32_t samples = 16*256;
    cl::make_kernel<cl_uint,cl::Buffer> Pointless(cl::Kernel(program,"Pointless"));
    cl::Buffer device_samples(device.context_,CL_MEM_READ_WRITE,sizeof(cl_uint)*samples);
    Pointless(cl::EnqueueArgs(device.queue_, cl::NDRange(16)), samples, device_samples).wait();

    std::vector<cl_uint> host_samples(samples);
    device.queue_.enqueueReadBuffer(device_samples,CL_TRUE,0,sizeof(cl_uint)*samples,host_samples.data());

    for (auto x: host_samples)
        std::cout << x;
    std::cout << std::endl;

    return 0;
}

以上似乎失败了:我在 enqueueReadBuffer 上遇到了段错误。更有趣的是，它只在 GPU(Intel P4000)上失败。 CPU (i3 3xxx) 运行它没有问题(将 CL_DEVICE_TYPE_GPU 更改为 CL_DEVICE_TYPE_CPU 以在 CPU 上进行测试)。

现在下面的代码适用于两种设备类型。

#include <iostream>
#include <CL/cl.hpp>

int main()
{
    std::vector<cl::Platform> platforms;
    cl::Platform::get(&platforms);
    cl::Platform platform = platforms[0];

    std::vector<cl::Device> devices;
    platform.getDevices(CL_DEVICE_TYPE_GPU, &devices);
    cl::Device device = devices[0];

    cl_context_properties properties[3] = {
        CL_CONTEXT_PLATFORM,
        (cl_context_properties)(platform)(),
        0
    };

    cl_int clErr = CL_SUCCESS;
    cl::Context context(device, properties, NULL, NULL, &clErr);

    cl::CommandQueue queue(context,device,0,&clErr);

    cl::Program::Sources source;
    std::string src =
    "__kernel void Pointless(uint total, __global uint *data)"\
    "{"\
    "   uint perStream=total/get_global_size(0);"\
    "   __global uint *dest=data+get_global_id(0)*perStream;"\
    "   for(uint i=0;i<perStream;i++)"\
    "       dest[i] = 1;"\
    "}";

    source.push_back({src.c_str(),src.length()});

    cl::Program program = cl::Program(context,source,&clErr);

    clErr = program.build({device});
    if(clErr != CL_SUCCESS)
    {
        std::cerr << program.getBuildInfo<CL_PROGRAM_BUILD_LOG>(device) << std::endl;
    }

    uint32_t samples = 16*256;
    cl::make_kernel<cl_uint,cl::Buffer> Pointless(cl::Kernel(program,"Pointless"));
    cl::Buffer device_samples(context,CL_MEM_READ_WRITE,sizeof(cl_uint)*samples);
    Pointless(cl::EnqueueArgs(queue, cl::NDRange(16)), samples, device_samples).wait();

    std::vector<cl_uint> host_samples(samples);
    queue.enqueueReadBuffer(device_samples,CL_TRUE,0,sizeof(cl_uint)*samples,host_samples.data());

    for (auto x: host_samples)
        std::cout << x;
    std::cout << std::endl;

    return 0;
}

显然我在这里遗漏了一些非常基本的东西。他们都在使用 Intel ICD(我在这个系统上没有 AMD 设备)。

Answer 1

(刚开始发帖所以还不能评论)

我使用 Nvidia 实现(通过 Intel ICD 使用)测试了您的代码。 C++ 编译器是 G++ 4.7.3。您的两个示例在 GPU 以及可用的 Intel CPU 上都运行良好。

因此几乎可以肯定该问题仅限于 Intel GPU 实现。