Re: Converting strings to enum values (C API)

[Philipp Janda <siffiejoe@...>]

Am 05.12.2013 19:59 schröbte Tom N Harris:
> On Thursday, December 05, 2013 09:45:06 AM Marc Lepage wrote:
> > I guess I'd still be looping (or if-else-if-ing) over a list of pointers
> > for which to compare, if I can't statically embed that dispatch as a switch
> > statement (the pointers vary at runtime). Better than a strcmp, but now I'm
> > thinking a table of string-to-integer is probably going to be best.
>
> The cost of building the table may dominate runtime if the function is called
> infrequently. So perhaps you'd want to only memoize strings that are being
> used. And don't forget bsearch if you can promise the C array will be sorted.

Micro benchmark:
*   10 different options
*   each option name is 10 bytes long.
*   2000000 calls for each option name (so 20 million calls total)

luaL_checkoption	1.42	seconds
bsearch + memcmp	1.24	seconds
bsearch + strcmp	1.29	seconds
upvalue table	0.94	seconds


So, yeah, the lookup table in an upvalue is fastest here, but you need a 
few million calls to notice ...

Philipp