mesa Documentation

Introduction

For many large applications C++ is the language of choice and so it seems reasonable to define C++ bindings for OpenCL.

The interface is contained with a single C++ header file cl.hpp and all definitions are contained within the namespace cl. There is no additional requirement to include cl.h and to use either the C++ or original C bindings it is enough to simply include cl.hpp.

The bindings themselves are lightweight and correspond closely to the underlying C API. Using the C++ bindings introduces no additional execution overhead.

For detail documentation on the bindings see:

The OpenCL C++ Wrapper API 1.1 (revision 04) http://www.khronos.org/registry/cl/specs/opencl-cplusplus-1.1.pdf

Example

The following example shows a general use case for the C++ bindings, including support for the optional exception feature and also the supplied vector and string classes, see following sections for decriptions of these features.

#define __CL_ENABLE_EXCEPTIONS

#if defined(__APPLE__) || defined(__MACOSX)
#include <OpenCL/cl.hpp>
#else
#include <CL/cl.hpp>
#endif
#include <cstdio>
#include <cstdlib>
#include <iostream>

 const char * helloStr  = "__kernel void "
                          "hello(void) "
                          "{ "
                          "  "
                          "} ";

 int
 main(void)
 {
    cl_int err = CL_SUCCESS;
    try {

      std::vector<cl::Platform> platforms;
      cl::Platform::get(&platforms);
      if (platforms.size() == 0) {
          std::cout << "Platform size 0\n";
          return -1;
      }

      cl_context_properties properties[] = 
         { CL_CONTEXT_PLATFORM, (cl_context_properties)(platforms[0])(), 0};
      cl::Context context(CL_DEVICE_TYPE_CPU, properties); 

      std::vector<cl::Device> devices = context.getInfo<CL_CONTEXT_DEVICES>();

      cl::Program::Sources source(1,
          std::make_pair(helloStr,strlen(helloStr)));
      cl::Program program_ = cl::Program(context, source);
      program_.build(devices);

      cl::Kernel kernel(program_, "hello", &err);

      cl::Event event;
      cl::CommandQueue queue(context, devices[0], 0, &err);
      queue.enqueueNDRangeKernel(
          kernel, 
          cl::NullRange, 
          cl::NDRange(4,4),
          cl::NullRange,
          NULL,
          &event); 

      event.wait();
    }
    catch (cl::Error err) {
       std::cerr 
          << "ERROR: "
          << err.what()
          << "("
          << err.err()
          << ")"
          << std::endl;
    }

   return EXIT_SUCCESS;
 }