Re: ANN: sleep() patch for Lua 4.0
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- Subject: Re: ANN: sleep() patch for Lua 4.0
- From: "Thatcher Ulrich" <tu@...>
- Date: 2001年12月10日 18:16:15 -0500
On Dec 10, 2001 at 02:36 -0800, Steve Dekorte wrote:
>
> This is great. Is there any way to execute n number of instructions
> before going to sleep?
Not as it stands. That would be fairly simple to add.
I didn't want to tackle that the first time out though, because it
wasn't on my personal wishlist. Mainly because pre-emptive
multitasking is much trickier to debug (on the scripting side) than
cooperative multitasking, since it's less predictable and gets you
into all kinds of race conditions -- a scary situation for script
programmers!
But given those caveats, lua_sleep() makes it pretty easy to add. As
simple as:
if (L->oplimit && ++L->opcounter >= L->oplimit) {
L->opcounter = 0;
lua_sleep(L);
}
at the very bottom of the luaV_execute() loop (or just before the
instruction fetch), plus some code to initialize and access opcounter
and oplimit. Set oplimit to non-zero to enable it.
> Is there a hook that get's called when sleep is
> called?
Nope. I don't think it would be hard to add, but I haven't paid much
attention to how callbacks work in Lua. What would you use it for?
> I'm interested in playing around with actor-based programming techniques
> in Lua where every object has it's own "thread" of execution. Real
> threads would be much to heavy, but emulating threads by putting an
> object to sleep and switching to the next active object might work.
Yeah, definitely. I prefer the explicit cooperative approach because
of those race issues, but I don't see any reason the preemptive
approach wouldn't work, Lua-wise.
--
Thatcher Ulrich <tu@tulrich.com>
http://tulrich.com