Attached is an OpenCL kernel that triggers an awkward bug in Intel's OpenCL platform. On the same CPU it works on the AMD OpenCL platform, but not on the Intel OpenCL platform. This has been verified on multiple independent machines (all windows 7, both 32-bit and 64-bit). I have also added a tiny Netbeans project (with JOCL embedded) to provide full code to reproduce the bug. But if you don't use Netbeans, it's easy to reproduce anywhere by just feeding an empty float to the kernel and reading it afterwards.
What the program does is simply executing the same program 4 times. What should happen is obviously that you get always the same output. However, on the Intel platform, somehow suddenly the first execution yields a different result. Always consequently the first, always consequently the same wrong output, on different machines. But the kernel itself is pretty trivial and has no memory at all over different executions.
I would classify this as a severe bug, since it doesn't just crash, but instead provides erroneous output without any notice!