Re: Another attempt at SpeedingUpStrings
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- Subject: Re: Another attempt at SpeedingUpStrings
- From: Mark Hamburg <mhamburg@...>
- Date: 2007年12月17日 20:31:06 -0800
on 12/17/07 12:36 PM, Luiz Henrique de Figueiredo at lhf@tecgraf.puc-rio.br
wrote:
>> using pushstring() feels unoptimal.
>
> That's the problem: it *feels* unoptimal but in reality, as Rici reported,
> it does not make any actual difference, not enough to warrant a complicated,
> error-prone, ugly API...
>
> Yet another lesson at the wrong perceptions that we programmers have about
> performance...
I've done profiles where string pushing rated surprisingly high given that
Lightroom isn't a string intensive app. Not huge, but more than one would
expect. (Sorry. I can't recall numbers just now.)
On the other hand, changing luaB_type to use upvalues slashed some of that
away.
Mark
----
static int luaB_type (lua_State *L) {
luaL_checkany(L, 1);
lua_pushstring(L, luaL_typename(L, 1));
return 1;
}
#if ADOBE_EXTENSIONS
#define MIN_LUATYPE LUA_TNIL
#define MAX_LUATYPE LUA_TTHREAD
static int luaB_type_optimized (lua_State *L) {
int ltype = lua_type(L, 1);
if (MIN_LUATYPE <= ltype && ltype <= MAX_LUATYPE) {
lua_pushvalue(L, lua_upvalueindex(ltype + (1 - MIN_LUATYPE)));
return 1;
} else {
/* Fall back to non-optimized version. */
return luaB_type (L);
}
}
/* Takes the target table on the top of the stack. */
static void register_optimized_type (lua_State *L) {
int i;
for (i = MIN_LUATYPE; i <= MAX_LUATYPE; ++i) {
lua_pushstring (L, lua_typename(L, i));
}
lua_pushcclosure(L, luaB_type_optimized, MAX_LUATYPE - MIN_LUATYPE + 1);
lua_setfield(L, -2, "type");
}
#endif