Re: [boost] [math][distributions] superfluous checking ofparameters?

Subject: Re: [boost] [math][distributions] superfluous checking ofparameters?
From: Thijs (M.A.) van den Berg (thijs_at_[hidden])
Date: 2011-10-31 09:32:10

>>> * If the current policy (a template param) is to throw on domain errors (the default), then the second check in the non-member functions is redundant as any errors will have triggered an exception in the distribution constructor. On the other hand:
>>> * If the current policy is to not throw (return NaN on domain errors), then the constructor checks are redundant and the non-member function checks are the required ones.
>>> 
>>> If it really is a performance bottleneck, then we could add a check on the current exception policy so that those two mutually exclusive options get optimized at compile time.
>> 
>>> From a performance point of view, suppose I wanted to have a Policy mechanism that allows me to eliminate *all* error checking machine instructions from a distribution constructor of distribution non member function.
>> 
>> Would it be possible to move the detail::check_scale(d) etc into the Policy class? That way I could provide a different policy that get's eliminated compile time via an implementation like
>> "inline policy::check_scale(d){return;}"
> 
> I don't think we could move all the checks inside the policy class as each distribution is more or less different, but we could pass a compile time param to the checking functions to have the same effect.  In fact can you file a bug report so I don't forget?
> 
> Cheers, John. 

Thanks, I will file that. A good solution, I'm going to adapt that too