[To the Mods: I'm unsure whether I have posted under the right forum section. Please move this if I am. ]


I know there are quite a few that are entertained by the book authors' delegate library choice and it's possible alternatives. I myself have asked the question of the practicality in an alternative implementation where std::function + some sort of identifier are used instead of Don Clougston's FastDelegate library (in this post). I've since implemented said approach in my framework and realized that at the end of the day, a comparable delegate object is much more elegant than std::function which does not support comparison between 2 std::function's.

Not being able to compare delegates is a huge pain in the butt to register and de-register static class function and free functions, but std::function's lambda support is very desirable. I ended searching for other modern delegate library alternatives that are high performance, is comparable and provide lambda support, and was able to find the following that supports some if not all of the requirements:

• FastDelegate C++11 (a C++11 re-implementation of FastDelegate)
  
• ssuv::FastFunc (a different C++11 adaptation of FastDelegate)
  
• SRDelegate C++11 (a C++11 re-implementation of SRDelegate)
  

I've created a performance benchmark comparing these new libraries plus std::function, the original FastDelegate and raw function calls on GitHub (link ). Both a QtCreator project and a Visual Studio 2013 solution are provided. Some workarounds are added for the C++11 versions of the libraries due to Visual Studio's poor C++11 conformance.

The benchmark creates delegates for member functions, static class functions and static free functions and timed their operator() performance over 100 million calls. Here are the results for the MinGW(4.8.1?) and VC++12:





It is quite amusing to see that for this benchmark, the original FastDelegate does not perform any better than std::function (it is in fact worst in some scenarios). I am also surprised that the VC build does not perform better than the MinGW build.

All source is available on GitHub (link) including links to library source.

UPDATE(2014/07/12): The libraries are now also available in this repo (link), I've also updated the benchmark with fixes and updated libraries.

Originally posted by DieselMaxPower
I'll probably keep std::function just because it's easier to find support and doesn't introduce a library dependency, but this is good info!

I would have agreed with you several months ago, but not any more.

The only dependency that you would introduce to your project by using most of these libraries is only 1 header files. From an ease of use and performance stand point, std::function is at the bottom of the list. What kind of support do you need if they work out of the box? The C++11 versions of these libraries are only several hundred lines of code (ignoring my VC workarounds), I would rather maintain that myself than waiting for STL maintainers to fix any bugs. Especially if it was a Visual Studio one.

I will be replacing std::function with either ssvu::Fastfunc or SRDelegate in my framework. Last time I checked, the C++11 implementation of SRDelegate is still actively being maintained (or at least the chunk that it belongs to is anyway).

EDIT: remove double quote.