Changes to restrictions are not backwards compatible

[loostrum]

I have some old tuning script that used a function to check the restrictions. When the way restrictions are handled was updated (I don't know when, it seems the changelog hasn't been updated in a while?), this stopped working. Was it intended to still work with legacy restrictions?

The issue is that a restrictions function used to receive a dict with the tuning parameters as keys, but now it only receive the tuning parameter values.

[benvanwerkhoven]

Hi Leon! I'm not entirely sure I understand the issue fully. Do you have a code snippet of the function in question?

[loostrum]

Hi! Of course, this is how we use a restrictions function:

kt.tune_kernel(<...>, restrictions=restrict)

where restrict is a function that used to be like this:

def restrict(p):
        n_global_per_warp = int(p["N_PER_BLOCK"] // p["block_size_y"])
        m_global_per_warp = int(p["M_PER_BLOCK"] // p["block_size_z"])
        if n_global_per_warp == 0 or m_global_per_warp == 0:
            return False

To make it compatible with the new kernel tuner, we changed it to:

def restrict(*args):
        param_names = list(tune_params.keys())
        assert len(args) == len(param_names)
        p = {}
        for i in range(len(param_names)):
            p[param_names[i]] = args[i]

        n_global_per_warp = int(p["N_PER_BLOCK"] // p["block_size_y"])
        m_global_per_warp = int(p["M_PER_BLOCK"] // p["block_size_z"])
        if n_global_per_warp == 0 or m_global_per_warp == 0:
            return False

[benvanwerkhoven]

Thanks for bringing this to my attention! I wasn't aware that this change has crept in and I believe the current behavior is actually not what we want. I'm marking this as a bug. You can consider the current code that you have as a workaround until this is fixed.

[stijnh]

I've also ran into this problem! I look through the code, but not exactly sure what causes it.

Here, it is called as restriction(params):

kernel_tuner/kernel_tuner/util.py

Line 315 in 5a48c0b

valid = restrictions(params)

Here, it is called as restriction(**params):

kernel_tuner/kernel_tuner/util.py

Line 286 in 5a48c0b

return restrict(**params)

Here, it is directly converted into a FunctionConstraint:

kernel_tuner/kernel_tuner/searchspace.py

Line 511 in 5a48c0b

restriction = FunctionConstraint(restriction, required_params)

But here, it is converted via a wrapper that convert the arguments back into a dict:

kernel_tuner/kernel_tuner/searchspace.py

Lines 531 to 534 in 5a48c0b

	def restrictions_wrapper(*args):
	return check_instance_restrictions(restrictions, dict(zip(self.param_names, args)), False)
	parameter_space.addConstraint(FunctionConstraint(restrictions_wrapper), self.param_names)

[fjwillemsen]

@loostrum I've fixed this now in this branch: https://github.com/KernelTuner/kernel_tuner/compare/fix_issue_333. I've also added a test to prevent this problem in the future. Are you in a position to check whether this resolves your issue? If not it will be included in the next release.

[loostrum]

@fjwillemsen In your branch the issue is fixed indeed, thanks!