I have developed a probabilistic sampling program that made use of the "lgamma" function in OpenCL. The program runs normally on most platforms, including Intel's CPU using Intel's OpenCL driver. However, on the integrated HD 4000 and HD 4400, the program fails to produce the correct values. After a little debugging, I've identified that the value of the "lgamma" function is computed incorrectly when the OpenCL program is run on HD 4000/4400. The problem exists under Windows 7, 8, and 10 (preview), using the latest graphics driver (ver. 4098, dated 1/19/2015).
It seems that the problem has been reported before:
https://software.intel.com/en-us/forums/topic/468324
I don't have HD 5000 and up for testing. So I can't say much about those parts.
Under Linux, this problem doesn't exist using the open source Beignet package. So this doesn't seem to be a hardware issue.
We would greatly appreciate a fix since this problem has prevented us from deploying our toolkit to any users with only intel HD gpus.
Thanks!