Re: [boost] [function] function wrapping withnoexceptionsafetyguarantee

Subject: Re: [boost] [function] function wrapping withnoexceptionsafetyguarantee
From: Emil Dotchevski (emil_at_[hidden])
Date: 2010-11-06 14:08:34

On Sat, Nov 6, 2010 at 10:22 AM, Daniel Walker
<daniel.j.walker_at_[hidden]> wrote:
> On Tue, Nov 2, 2010 at 7:20 PM, Jeffrey Lee Hellrung, Jr.
> <jhellrung_at_[hidden]> wrote:
>> On 11/02/2010 02:50 PM, Daniel Walker wrote:
>> [...]
>>>
>>> Here are the results I got, again, using the build of g++ 4.2 provided
>>> by my manufacturer.
>>>
>>> Data (Release):
>>>            |  function   | function (static empty)
>>> time/call  |  3.54e-07s  |  3.51e-07s
>>> space/type |    64B      |    80B
>>>
>>> Data (Debug):
>>>            |  function   | function (static empty)
>>> time/call  |  2.05e-06s  |  2.04e-06s
>>> space/type |    64B      |    80B
>>>
>>> You can see that removing the empty check from boost::function yields
>>> about a 1% improvement in time per call to boost::signal. The
>>> increased space per type overhead is the same as before: 16B.
>>
>> [...]
>>
>> [Butting in after only vaguely following this thread...]
>>
>> Would it also be appropriate to measure the "space/call", in addition to
>> "time/call" and "space/type"?  Or is there no difference, or had this been
>> addressed already?
>
> Well, a call to boost::function does not cost any additional space.
> However, there is a space/object cost, which the other benchmark does
> measure. The space overhead per boost::function object is constant. On
> my machine it's 32B for both of the empty state schemes.

Can someone please explain why does storing the empty state take space per type?

Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode