[SOLVED] OpenCl is a Library or is a Compiler?

OpenCl is a Library or is a Compiler?

I started to learn OpenCl. I read these links:

https://en.wikipedia.org/wiki/OpenCL
https://github.com/KhronosGroup/OpenCL-Guide/blob/main/chapters/os_tooling.md
https://www.khronos.org/opencl/

but I did not understand well that OpenCl is a library by including header file in source code or it is a compiler by using OpenCl C Compiler?!

Solution

It is both a library and a compiler.

The OpenCL C/C++ bindings that you include as header files and that you link against are a library. These provide the necessary functions and commands in C/C++ to control the device (GPU).

For the device, you write OpenCL C code. This language is not C or C++, but rather based on C99 and has some specific limitations (for example only 1D arrays) as well as extensions (math and vector functionality).

The OpenCL compiler sits in between the C/C++ bindings and the OpenCL C part. Using the C/C++ bindings, you run the compiler at runtime of the executable with the command clBuildProgram (C bindings) or program.build(...) (C++). It then at runtime once compiles the OpenCL C code to the device-specific assembly, which is different for every vendor. With an Nvidia GPU, you can for example look at the Compiler PTX assembly for the device.