Re: Lua vm call speed

[herviou <herviou@...>]

thanks,

actually the first time I call lua I open a state  and load/compile the 
script then
every time I call lua I do it this way (in your "not to do list"):

   lua_pushstring(L,"funToRun")

   lua_gettable(L,LUA_GLOBALSINDEX)

   ...push args

   lua_pcall(L,...)  --that is what I mean by ''call''


I have also try to measure the time of this from beginning to the end,
I mostly obtain several million calls per second as you mentionned but 
sometimes it takes 0.01 sec of execution (this loop).
I have try to see if it corresponds to a garbage collection cycle by 
stopping it but didn't change anything.
Having 0.01 sec sometimes for one lua vm is not a problem but when 
running an hundred of lua vm it's a little bit too much.

bye,
   dh





Mike Pall wrote:

> Hi,
>
> herviou wrote:
>  
>
> > This weekend I have 
> > pointed out that it can cost a non negligeable time to call the lua vm. 
> >    
>
> Umm, this is usually not an issue? Lua can do several million
> calls per second on a (slow) Pentium III.
>
> Maybe your definition of "call" is different. Parsing a script
> should only be done once (and closures created only once, too).
> The resulting functions should be put into a table or an upvalue
> of a C closure.
>
> Something like:
>
>  ... loop ... {
>    lua_rawgeti(L, table_idx, idx);  // Push table outside loop/use upvalue
>    ... or ...
>    lua_pushvalue(L, lua_upvalueindex(idx));  // For low # of functions
>    ...
>    lua_call(L, nargs, nresults);
>  }
>
> But avoid doing any of these on every iteration:
>
>  lua_open() ... lua_close()      // Recreates a Lua universe every time.
>  lua_load()/luaL_load*()         // Loads/parses a script every time.
>  lua_pushcfunction()/lua_pushclosure() // Creates a C closure every time.
>  lua_getglobal()/lua_setglobal() // Accesses a global every time.
>
>
> There are more things to avoid on the Lua side of the code, too.
> There's a Wiki page: http://lua-users.org/wiki/OptimisationTips
>
> Even more ideas can be found by reading through fully optimized
> Lua code. Shameless plug (I wrote most of these):
> http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=lua&lang2=lua
>
>  
>
> > I'm working with Lua for creating IA in virtual drivers in a
> > traffic road simulator.
> >    
>
> BTW: this sounds like you should investigate Lua coroutines, too.
> Look through the archive about Lua coroutines for AI in games.
>
> Bye,
>     Mike
>
>  
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