Re: [boost] [Signals] Named slot group usage?

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-02-11 13:34:05

On Feb 11, 2005, at 11:49 AM, Peter Dimov wrote:

> Doug Gregor wrote:
>> On Feb 11, 2005, at 9:51 AM, Peter Dimov wrote:
>>
>>> Douglas Gregor wrote:
>>>> Background: Signals performance is sub-par, and much of the problem
>>>> can be traced back to support for named slot groups. I'm trying to
>>>> determine the best way to proceed.
>>>
>>> Are you sure that this is the case?
>>
>> There may be other issues, but going from a std::list to a std::map
>> (as needed to efficiently support connection of named slots) hurts
>> iteration performance and increases executable code size. To counter
>> the latter problem, I've done some type erasure that slows it down
>> further and causes some of the extra heap allocations :(
>
> You mean disconnection of named slots, right? List connection is O(1), 
> map - O(log N). You get ordering for free with a map, sure, but this 
> is a separate issue.

Both connection and disconnection of named slots are O(lg N), since we 
need to keep the whole list ordered when named slots are present. 
Connection/disconnection of unnamed slots is O(1) now.

Iterating through a map really is slow, though... loops in operator++ 
really hurt us. I've tried a few times to come up with some ultra-slick 
formulation using a list for primary storage and a map indexing into 
the list... but I've always failed to deal with the iterator 
invalidation issues.

> Anyway, I'm sure that few people would miss named slots.

That's what I'm trying to figure out; but I suspect that you're right.

>  Lets' drop them. :-)

You're not the only one to say that :)

        Doug