Intel® VTune™ Profiler User Guide

User Guide

Contents

Error Message: Not All OpenCL™ API Profiling Callbacks Are Received

Cause

Intel® VTune™ Profiler uses OpenCL™ API to collect profiling information about OpenCL kernels. According to the OpenCL Specification, completion callbacks must be thread-safe and can be called in different threads. It is possible that the completion callback is received while the collection is being stopped.

Solution

Use OpenCL API to set callbacks for events for
clEnqueue*
 functions and wait for them to be received. For example: 
#include <atomic>
#include <thread>
...
#include <CL/cl2.hpp>

std::atomic_uint32_t number_of_uncompleted_callbacks = 0;

void CL_CALLBACK completion_callback(cl_event, cl_int , void*)
{
     --number_of_uncompleted_callbacks; 
}
int main()
{
    ...
    cl::Program prog(context, 
        std::string((std::istreambuf_iterator<char>(programSourceFile)),std::istreambuf_iterator<char>()));
    ...
    auto kernelFunc = cl::KernelFunctor<cl::Buffer, cl_int>(prog, "sin_cos"); 
    cl::Event event = kernelFunc(cl::EnqueueArgs(cl::NDRange(dataBuf.size())), clDataBuf, 0);

    ++ number_of_uncompleted_callbacks;
    event.setCallback(CL_COMPLETE, completion_callback);
    ...
    while (number_of_uncompleted_callbacks.load())
    {
        std::this_thread::yield();
    }
    return EXIT_SUCCESS;
}

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.