Tuesday, February 21, 2012

Linking OpenCL - Oh, wait ...

Latest work from Danilo, my Chilean tessellation friend!
OpenCL is a nice way to utilize vector processors or multi cores.
But when it comes to writing and linking our software against a OpenCL it doesn't seem to open anymore. Because currently you need to link to one specific OpenCL implementatio, like AMD's or Intel's.
Okay, that might in the normal case not be to problematic, but as Fedora Packager I don't want to link some software to one specific implementation, if there are several.
This problem already appeared to the arch people and they just pulled the - so called - ICD loader out of one of the available implementations into the libCL package, to solve this problem.

ICD loader
So how does this help? ICD is a mechanism specified by Khronos to allow several OpenCL implementations to be installed side-by-side without disturbing each other. And the ICD loader allows to freely choose between one of the available ones (if it supports ICD), as the loader redirects the API calls to the choosen implementation.

What we need is some kind of just-an-ICD-loader which provides /lib64/libOpenCL.so which is the in turn using the actual implementation (e.g. pocl or the upcoming nouveau / clover [hopefully AMD to] thing).

There are already some open ICD implementations available, maybe those can be reused.

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