Re: Faster checking of userdata

[Shannon Stewman <stew@...>]

On Thu, Aug 26, 2004 at 07:31:14PM -0300, Fabio Mascarenhas wrote:

> Hmm, did you benchmark this? I would be surprised if your function is 
> faster than luaL_checkudata, because luaL_getmetatable uses 
> lua_pushstring. This function is pretty costly, compared to lua_rawget 
> and strcmp (it does a strlen and computes a hash of the string).

I did, in fact benchmark this, and it reduces the time spent in various
functions from 60% down to less than 1%.  The total time spent in
fastcheckudata is around 2% of the total program time, compared with
13-15% in luaL_checkudata.  It makes sense; luaL_checkudata also uses a
luaL_getmetatable, and the profiler reported that a large chunk of time
spent in luaL_checkudata was spent in strcmp.

> Your best bet is to use a light userdata to identify your metatables, 
> like the other poster suggested, instead of a string.

Thank you both for the suggestion!

-- 
Shannon Stewman         | Let us walk through the waning night,
Caught in a whirlpool,  | As dawn-rays tickle our toes, the dew soothes
A quartering act:       | Our blistered soles, and damp bones stir
Solitude or society?    | As crimson cracks under the blue-grey sky.