This is just a re-post of my thread on the nvnews forums, after I was told I’d probably get better help if I asked here instead.
This isn’t a user question, it’s a developer question. I already know that OpenCL works fine on my system because I’ve successfully run some simple test apps. I’m just having trouble writing my own OpenCL code using nVidia’s drivers. Dunno if this is the right place to go for developer help, but I’ll ask here anyway so I don’t get flamed if I ask on the Knronos forums.
I am trying to implement my own OpenCL ICD Loader (implementing this spec.) The use case is that it will be statically linked with an application and will detect any OpenCL ICDs installed on the system.
According to the spec (at least, as I understand it,) /etc/OpenCL/vendors/*.icd is a file with the name of a .so; the .so will provide an OpenCL implementation which the ICD Loader will load. In this case, I have /etc/OpenCl/vendors/nvidia.icd, which references “libcuda.so,” which I can open just fine with dlopen(). I can get clGetExtensionFunctionAddress and clGetPlatformInfo from libcuda.so using dlsym(), and I can then use clGetExtensionFunctionAddress to retrieve clIcdGetPlatformIDsKHR. I can then use clIcdGetPlatformIDsKHR and clGetPlatformInfo to query all platforms provided by the driver (all one of them) and verify that they all support the cl_khr_icd extension. So far it’s going exactly like the spec says it should.
However, libcuda.so does not seem to export any of the rest of the OpenCL API- clGetDeviceIDs, clGetDeviceInfo, etc. etc. etc.-- dlsym fails on all of them. In addition, I cannot get any of them with clGetExtensionFunctionAddress either, I’ve tried.
Am I misunderstanding the spec? Should I be looking elsewhere for these functions? If any nVidia developers are reading this, would they mind disclosing how nVidia’s ICD loader does this?
For now, I’m just having it fall-back to libOpenCL.so if it detects an invalid ICD, and I have it working correctly that way, but I’d like to get it working this way as well (it is an ICD loader after all, not just a wrapper.)
- [*]32-bit Linux Mint 9 (Ubuntu 10.04)
Driver 195.36.24 from nvidia-current package
Browse source code:
Zipped format download:
The part you are probably most interested in is clicd_locateicd_unix.c, which contains all the code being discussed here.
Pure ANSI C, includes README, Makefile, and test applications, no dependencies. “make testapps” to compile it, then you can “cd testapps” and run the three tests:
It should also be trivially easy to compile on OS X, but I have not tested it there yet. For Windows, you would need to add code to look for registry keys to find the ICDs, as described by the spec.