[Stackless] lua vs. stackless python
senn at maya.com
Fri Apr 24 16:30:06 CEST 2009
On Apr 23, 2009, at 4:36 PM, Richard Tew wrote:
> Whether someone would choose Lua or Stackless Python for coroutines is
> probably a matter of preference for the language itself. But one
> thing Stackless might provide that Lua does not, is the ability to
> block C function calls as well as Python function calls given that we
> shift C stack sections in and out with tasklets. Or the ability to
> persist and unpersist in a cross platform way, running tasklets.
To clarify a couple of points:
> Stackless, going from my limited understanding here, is not
> 'actually stackless' at all -- but by manipulating the C stack,
> allows dynamic switching between (arbitrary?) frames. I have read
> that lua is 'literally stackless', and does not use a C stack at
> all... correct? Please, scientists and engineers, tell me what this
> means to me...
Stackless does use the C-stack, but sparingly, and except for when C
extensions call back into python,
it is "unrolled" between task switching. So essentially it is "C
stackless" in (dare I say) *most* cases.
When there *are* extension callbacks -- then the C-stack needs to be
copied and dynamically patched.
So it's sort of the best of both worlds.
> Stackless's 'tasklets' weigh only a few kilobytes a piece; what does
> a lua coroutine weigh?
When there are extension callbacks the stackless tasklets *could* be
much more weighty...
depending one what is on the stack.
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