CODEWITHSUNDEEP
c++opencl
alonelycoder
alonelycoder

Reputation: 103

Unable to display <CL_DEVICE_MAX_WORK_ITEM_SIZE> in OpenCL and C++

I am new to OpenCL and I have a problem with displaying the <CL_DEVICE_MAX_WORK_ITEM_SIZES> as a whole number/value. Instead I get a memory address.

Initially, I tried to declare a string and integer output variable to display the maximum work item size. But eventually I found out that the work item size returns a size_t data type instead. So I created a vector to store the size_t variable but it outputs a memory address instead.

And also, my display shows the Device Number in the reverse order (shows Device #1 then Device #0 - this is used to select a device for the later part of my program)

Any help would be appreciated. Thank you.

int main()
{
    std::vector<cl::Platform> platforms;    // available platforms
    std::vector<cl::Device> devices;        // devices available to a platform
    std::string outputString;               // string for output
    std::vector<::size_t> maxWorkItems[3];
    unsigned int i, j;                      // counters
    std::string choice;                     // user input choice

    cl::Platform::get(&platforms);
    std::cout << "Do you want to use a CPU or GPU device: ";
    std::cin >> choice;
    if (choice == "CPU" || choice == "cpu")
    {
        // for each platform
        for (i = 0; i < platforms.size(); i++)
        {
            // get all CPU devices available to the platform
            platforms[i].getDevices(CL_DEVICE_TYPE_ALL, &devices);

            for (j = 0; j < devices.size(); j++)
            {
                cl_device_type type;
                devices[j].getInfo(CL_DEVICE_TYPE, &type);
                if (type == CL_DEVICE_TYPE_CPU) {
                std::cout << "\tDevice #" << j << std::endl;
                //outputs the device type
                std::cout << "\tType: " << "CPU" << std::endl;
                // get and output device name
                outputString = devices[j].getInfo<CL_DEVICE_NAME>();
                std::cout << "\tName: " << outputString << std::endl;
                // get and output device vendor
                outputString = devices[j].getInfo<CL_DEVICE_VENDOR>();
                std::cout << "\tVendor: " << outputString << std::endl;
                //get and output compute units
                std::cout << "\tNumber of compute units: " << devices[j].getInfo<CL_DEVICE_MAX_COMPUTE_UNITS>() << std::endl;
                //get and output workgroup size
                std::cout << "\tMaximum work group size: " << devices[j].getInfo<CL_DEVICE_MAX_WORK_GROUP_SIZE>() << std::endl;
                //get and output workitem size
                maxWorkItems[0] = devices[j].getInfo<CL_DEVICE_MAX_WORK_ITEM_SIZES>();
                std::cout << "\tMaximum work item size: " << maxWorkItems << std::endl;
                //get and output local memory size
                std::cout << "\tLocal memory size: " << devices[j].getInfo<CL_DEVICE_LOCAL_MEM_SIZE>() << std::endl;
                std::cout << std::endl;
            }
        }
    }
}

Below is the undesired output of my code: The max work item size is in hexadecimal format, and the device numbers are in reverse order. output

Upvotes: 3

Views: 1632

Answers (1)

pmdj
pmdj

Reputation: 23438

The CL_DEVICE_MAX_WORK_ITEM_SIZE property is of array type, specifically, size_t[]. You shouldn't be expecting a scalar value, but an array of CL_DEVICE_MAX_WORK_ITEM_DIMENSIONS elements. With the OpenCL C++ wrapper, you're on the right track with the vector, but you've now declared an array of 3 vectors:

std::vector<::size_t> maxWorkItems[3];

You in fact just want the one vector that will hold all the returned values:

std::vector<::size_t> maxWorkItems;

The property query becomes:

maxWorkItems = devices[j].getInfo<CL_DEVICE_MAX_WORK_ITEM_SIZES>();

Then you should be able to query the max work items in each dimension using maxWorkItems[0], maxWorkItems[1], etc.

Upvotes: 3

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