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From: Dave Moore (jdmoore99_at_[hidden])
Date: 2005-12-23 07:35:52

> Signals is much slower than vector<function<...> > because it has to do
> a lot more work than vector<function<...> >. Much of the problem comes
> from the fact that one can disconnect slots from a signal while that
> signal is invoking slots. A comparison against something like
> list<pair<function<...>, bool> >, where the bool tells us if we should
> skip the slot or not, would give us a much better bound on the
> performance that could be achieved by Signals.
> That said, named_slot_map::iterator is horrible for performance. It was
> built that way to decrease the object-file size for programs using
> Signals, named slots are just plain expensive. I think we can build a
> data structure that allows the implementation of the slot list to be
> similar to list<pair<function<...>, bool> >, with the mappings from
> named slots to position in the list stored in a separate data
> structure... but nobody has implemented this yet. My attempts to kill
> named slots outright, thus improving the performance of Signals, have
> met much resistance.

An approach where the slot list is more list list<pair<function<...>, bool>
>, seems like a good step in the right direction. I appreciate the overhead
needed in providing clean disconnect semantics during signal callbacks...
I'd just like to see the named_slots overhead only 'hit' when actually using
the feature. It seems like a good application of pay-for-what-you-use.


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