Re: Identifiying which derived class you have in code
* James Kanze:
On Sep 12, 5:46 am, "Alf P. Steinbach" <al...@start.no> wrote:
* Christopher:
As always, remember to measure.
It might be that this attempt at optimization will have
little, no or even negative effect (such is difficult to
predict, measurement is needed).
It's rather obvious that maintaining code with 10 or more
dynamic_cast's is very expensive. I don't think you need to
measure that.
The alternative to optimization isn't another and extremely silly attempt at
optimization, it's simply to not optimize (manually), i.e. using a common
interface for everything regardless of whether there is a special case.
And then, relative to no optimization a check for special case will cause
branching, and it will most probably cause slightly (microscopically) larger
code size, which can influence caching, and with your proposed way of checking
(dynamic cast) instead of my proposed way of checking, the check itself will
likely be "expensive" relative to the code it guides.
Thus, the only way to be sure about the effect is to measure.
Cheers & hth.,
- Alf
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