OpenCL Platform Information Using C++ and CMake

Platform C Construct

Programming OpenCL in C++ is a wrapper to the C functions, the C function to initialize the platform structures is the following:

// Provided by CL_VERSION_1_0
cl_int clGetPlatformIDs(
    cl_uint num_entries,
    cl_platform_id* platforms,
    cl_uint* num_platforms);

The parameters of the function are the following

• num_entries is the number of cl_platform_id entries that can be added to platforms. If platforms is not NULL, num_entries must be greater than zero.
• platforms returns a list of OpenCL platforms found. The cl_platform_id values returned in platforms can be used to identify a specific OpenCL platform. If platforms is NULL, this argument is ignored. The number of OpenCL platforms returned is the minimum of the value specified by num_entries or the number of OpenCL platforms available.
• num_platforms returns the number of OpenCL platforms available. If num_platforms is NULL, this argument is ignored.

In C, the function has to be called twice. First to get the number of platforms and second to initialize the structures once allocated.

cl_platform_id *platforms;
cl_uint num_platforms;
clGetPlatformIDs(10, NULL, &num_platforms);
platforms = (cl_platform_id*)
malloc(sizeof(cl_platform_id) * num_platforms);
clGetPlatformIDs(num_platforms, platforms, NULL);

main.cpp

The following code section uses cl::Platform::get(&platforms); to collect all the platforms into a std::vector<cl::Platform>

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

int main() {
    // initialize a vector to store the platforms
    std::vector<cl::Platform> platforms{};

    // collect the platforms available
    cl::Platform::get(&platforms);

    // make sure at least we have a platform
    if (platforms.empty()){
        std::cerr << "No platforms found!" << std::endl;
        exit(1);
    }

    std::cout << "Number of platforms found: " << platforms.size() << std::endl;
    // iterate over each platform
    for (const cl::Platform& platform : platforms) {
        std::cout << "\tPlatform name: " << platform.getInfo<CL_PLATFORM_NAME>() << std::endl;
        std::cout << "\tPlatform vendor: " << platform.getInfo<CL_PLATFORM_VENDOR>() << std::endl;
        std::cout << "\tPlatform version: " << platform.getInfo<CL_PLATFORM_VERSION>() << std::endl;
        std::cout << "\tPlatform profile: " << platform.getInfo<CL_PLATFORM_PROFILE>() << std::endl;
        std::cout << "\tPlatform extensions: " << platform.getInfo<CL_PLATFORM_EXTENSIONS>() << std::endl;

        // collect the devices
        std::vector<cl::Device> devices;
        platform.getDevices(CL_DEVICE_TYPE_ALL, &devices);

        std::cout << "\tPlatform devices: " << devices.size() << std::endl;
        std::cout << "\n----------\n" << std::endl;
    }

    std::cout << "Done!" << std::endl;
    return 0;
}

CMakeLists.txt Code

cmake_minimum_required(VERSION 3.28)
project(OpenCL_PlatformInformation LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 17)

add_executable(${PROJECT_NAME} main.cpp)

find_package(OpenCL REQUIRED)
target_link_libraries(${PROJECT_NAME} OpenCL::OpenCL)

target_compile_definitions(${PROJECT_NAME} PRIVATE CL_HPP_TARGET_OPENCL_VERSION=300)

Program Output

This is the output of my current system:

Number of platforms found: 2
	Platform name: Clover
	Platform vendor: Mesa
	Platform version: OpenCL 1.1 Mesa 22.3.6
	Platform profile: FULL_PROFILE
	Platform extensions: cl_khr_icd
	Platform devices: 1

----------

	Platform name: rusticl
	Platform vendor: Mesa/X.org
	Platform version: OpenCL 3.0
	Platform profile: FULL_PROFILE
	Platform extensions: cl_khr_icd
	Platform devices: 0

----------

Done!

Process finished with exit code 0