Minimum version macros

[vchuravy]

This PR adds minimum version macros as discussed in #42, #49 and #40 based on a runtime check and caching of the result in a global dictionary.

They take the form of a ternary operator:

# E can be a variable of type Context, CmdQueue, Platform or Device
@min_v12 E begin 
    ....
end : error("Only supported since OpenCL 1.2")

to see how this might be used take a look at the branch https://github.com/JuliaGPU/OpenCL.jl/tree/vc/refactor_version_dependent_code

[jakebolewski]

This looks great. I think that this is a much simpler design. The only thing I would add is a finalizer hook to unregister the object pointer from the dict when it is gc'd.

[vchuravy]

Hm, when I add a finalizer I get the following error:

function check_version(elem, version :: VersionNumber)
    id = _get_id(elem)
    version <= get!(_versionDict, id) do
        finalizer(id, key -> delete!(_versionDict, key))
        opencl_version(elem)
    end
end

 objects of type Ptr{None} cannot be finalized

[jakebolewski]

The hook would included in the Platform, CmdQueue, etc object finalizers. The extra step would see if the object being finalized has an id in the dict and remove itself before returning.

[vchuravy]

But if you have two objects that reference to the same device/platform you would remove an entry unnecessarily. There is only a limited number of devices and platforms on the system so those shouldn't be a problem. The only object that would need a finalizer call would be Context since CmdQueue uses the id of the associated Device

[jakebolewski]

If two objects reference the same context pointer then one will not retain the context. The context object would only remove itself from the dict if it owns the underlying pointer.

[vchuravy]

@jakebolewski like so?

[jakebolewski]

@vchuravy exactly. The only other comment I have is that pointer should be defined so it may be cleaner to replace _get_id with pointer(CLObject).

[vchuravy]

@jakebolewski I agree that is certainly cleaner. I will then squash this and merge it.

Maybe we should also introduce and abstract type CLObject as a supertype of CmdQueue, Device, Context, and Platform so that one could dispatch opencl_version and check_version on it.

[jakebolewski]

Cool, all OpenCL objects sharing a common abstract subtype makes sense. We
could then get rid of the equality macro.

On Fri, Sep 5, 2014 at 1:49 PM, Valentin Churavy [email protected]
wrote:

@jakebolewski https://github.com/jakebolewski I agree that is certainly
cleaner. I will then squash this and merge it.

Maybe we should also introduce and abstract type CLObject as a supertype
of CmdQueue, Device, Context, and Platform so that one could dispatch
opencl_version and check_version on it.

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