How to define/use function in kernel

Question

Consider the following example:

std::string kernelCode =
    "void kernel copy(global int* image, global int* result)"
    "{"
        "result[get_global_id(0)] = foo(get_global_id(0));"
    "}";

sources.push_back({kernelCode.c_str(), kernelCode.length()});

cl::Program program(context, sources);

if (program.build({defaultDevice}) != CL_SUCCESS)
{
    std::cerr << "Error while building kernel: " <<
        program.getBuildInfo<CL_PROGRAM_BUILD_LOG>(defaultDevice) << std::endl;
    exit(1);
}
else
{
    qDebug() << "Kernel compiled succesfully\n";
}

How do I use or define a function like:

int foo(int id)
{
   //...
}

to use in the kernel?

If you develop a lot of code in OpenCL you should consider putting you kernel source in .cl files. This will allow you to use debugging tools and help with the legibility of your code. — OlivierLi
– OlivierLi, Commented Feb 10, 2014 at 20:12

yuri kilochek · Accepted Answer · 2014-02-10 19:56:19Z

1

Source can contain multiple functions, so simply prepend it:

std::string kernelCode =
"int foo(int id)"
"{"
"    return id + 1;"
"}"
"void kernel copy(global int* image, global int* result)"
"{"
"    result[get_global_id(0)] = foo(get_global_id(0));"
"}";

answered Feb 10, 2014 at 19:56

yuri kilochek

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