windows - Do I really need an OpenCL SDK?

Question

I just tried to make myself familiar with OpenCL but totally got confused when everyone in the Internet was talking about downloading a Vendor specific OpenCL SDK. Why would I need that?

My understanding of using OpenCL was the following:

1. Download the OpenCL header files that are maintained by Kronos in the Khronos OpenCL Registry and make it available to your compiler.
2. Compile your code and link against the OpenCL.dll.

The reason why it confuses me is because I thought that OpenCL should abstract away vendor specific implementations. If I now download a Vendor specific SDK isn't then this advantage destroyed?

Can someone please make this clear?

Answer 1

Your understanding is absolutely correct - you do not need any vendor SDKs in order to develop or run OpenCL programs. All you need are the headers and a library to link against. The vendor SDKs provide sample code that may be useful to look at while you are learning how to use OpenCL, and they may also provide tools that can aid development.

On Windows, you will need an OpenCL.lib library to link against, which the SDKs do provide. You can download the sources for this library and build it yourself if you wish.

There is no harm from using a specific vendor's SDK however. The headers and library that they provide in the SDK should just be the stock Khronos versions that you can download yourself. This means that an OpenCL application built using one vendor's SDK will still run just fine against other vendors' devices.