What is the difference between POCL(Portable Computing Language) and OpenCL?

Question

What is the difference between POCL(Portable Computing Language) and OpenCL, and what are the advantages POCL? http://pocl.sourceforge.net/

Does POCL have a C-like language, which is different from OpenCL, a different compiler (Clang> = 3.2), different backend (llvm), better portability, or something else?

And when we need to use the (hard-linking) OCL, and when need to use the ICD? http://streamcomputing.eu/blog/2013-07-08/installing-and-using-pocl/

Answer 1

Pocl is like any other opencl platform. It provides a opencl cpu device on x86/arm and many more systems. It is almost compliant to opencl 1.2 standards, except it doesn't have stuffs like cl_gl sharing etc. It uses clang/llvm to utilize all cpu cores and vector units in the cpu.

opencl is a spec and pocl implements this spec to give you a platform with cpu devices

coming to ICD, you link against ICD when you have more than one opencl platforms installed. Compile this icd code from khronos http://www.khronos.org/registry/cl/specs/opencl-icd-1.2.11.0.tgz and you will have an icd loader which can load any opencl platform. Hardlinking to a platform ".so" is possible say libpocl.so, but other installed platforms will not be visible in clGetPlatformIDs call. So ICD is better

Answer 2

OpenCL is a specification maintained by Khronos. There are many implementations, from vendors like AMD, NVIDIA, Intel, and Apple. In order to call itself an implementation of OpenCL a vendor must pass the conformance tests, be a member of Khronos, and probably some other things.

POCL (Portable Computing Language, formerly Portable OpenCL) is an open-source implementation of something very much like OpenCL but it is a work in progress and hasn't passed conformance tests so it's not really an implementation of OpenCL just yet. I gather they they aim to be one in the future, and wish them luck.

So there is your difference: one is a specification, the other aims to be an implementation of that specification.

I presume that POCL uses the same C99-based language for kernels, if they aim to be OpenCL compatible.

More on POCL at: http://pocl.sourceforge.net/