how to compile opencl project with kernels

Question

I am totally a beginner on opencl, I searched around the internet and found some \"helloworld\" demos for opencl project. Usually in such sort of minimal project, there is a *.c

Answer 1

My answer comes four years late. Nevertheless, I have something to add that complements @Farzad's answer, as follows.

Confusingly, in OpenCL practice, the verb to compile is used to mean two different, incompatible things:

• In one usage, to compile means what you already think that it means. It means to build at build-time, as from *.c sources to produce *.o objects for build-time linking.
• However, in another usage—and this other usage may be unfamiliar to you—to compile means to interpret at run time, as from *.cl sources, producing GPU machine code.

One happens at build-time. The other happens at run-time.

It might have been less confusing had two different verbs been introduced, but that is not how the terminology has evolved. Conventionally, the verb to compile is used for both.

If unsure, then try this experiment: rename your *.cl file so that your other source files cannot find it, then build.

See? It builds fine, doesn't it?

This is because the *.cl file is not consulted at build time. Only later, when you try to execute the binary executable, does the program fail.

If it helps, you can think of the *.cl file as though it were a data file or a configuration file or even a script. It isn't literally a data file, a configuration file or a script, perhaps, for it does eventually get compiled to a kind of machine code, but the machine code is GPU code and it is not made from the *.cl program text until run-time. Moreover, at run-time, your C compiler as such is not involved. Rather, it is your OpenCL library that does the building.

It took me a fairly long time to straighten these concepts in my mind, mostly because—like you—I had long been familiar with the stages of the C/C++ build cycle; and, therefore, I had thought that I knew what words like to compile meant. Once your mind has the words and concepts straight, the various OpenCL documentation begins to make sense, and you can start work.