Re: Design mistakes in mixed C/C++ and Lua projects

[Xavier Wang <weasley.wx@...>]

2011/10/21 Enrico Colombini <erix@erix.it>:
> On 21/10/2011 7.23, Miles Bader wrote:
>>
>> Thus, for operations which don't really need to be that fast,
>> individual calls from Lua into the core are fine, but for operations
>> where massive amounts of data need to be operated on, "bulk"
>> interfaces avoid the overhead of a large number of calls into the
>> core.
>
> One possible approach to minimize cross-language calls with plain Lua, which
> I adopted in 2D games, would be to divide responsibilities between a C++
> renderer/interpreter and high-level Lua logic.
>
> I kept rendering data on C++ side and gameplay data on Lua side; basically,
> a Lua function was called (or resumed) at each frame and did a brief amount
> of game logic (e.g. handle an event, start an animation, etc.), sending
> requests back to C++ through a streamlined API set. The requests (e.g.
> animate this image with such and such parameter) were then served on the C++
> side. On a given frame, there were only a handful of cross-language calls; I
> didn't even bother to optimize them.
> Long Lua operations were suspended and put into a resume queue handled by a
> C++ dispatcher.
> (it could also multitask on Lua side using coroutines, but I then limited it
> to one task per frame to reduce maximum frame time usage)
>
> So the engine ran in C++, but the game scripters only saw Lua (which allowed
> them to run their code almost immediately).
> It worked beautifully in a resource-limited handheld system (with a Lua
> budget of about 1 ms and 1 MB RAM, game data included).
>
> Of course there are many other possible approaches; system constraints and
> costs should be carefully weighted in the design phase.
>
> --
>  Enrico
>
>
OK, Just a question: Is crossing Lua/C bother fast in this situation:
All C functions Lua called and all Lua functions C called are only
have a few of arguments, of number, string and userdata. not else.

In this situation, is the Lua/C bother still slow? Do you have some
profile data? Sorry for I don't have idea to profile my project --
it's in a big C++ nut-shell :-(

To makes my game up to 60fps, there are still a lot of things to try...