Re: Raspberry Pi and Lua

[David Given <dg@...>]

steve donovan wrote:
[...]
> Well, support for Linux looks good [1], including Debian so Lua is
> just an apt-get away.

...Debian armel, so FPU performance is slow. (Both Debian and Ubuntu
target ARMv7+ only for the armhf variants with proper floating point
support. The Raspberry Pi has an ARMv6 processor in it.)

ARM floating point is a bit of a mess. There are multiple different
kinds of floating-point unit and two different ABIs for passing
floating-point registers, which are mutually incompatible. Historically,
floating-point registers got passed around in integer registers; this
made the ABI much easier but was dog-slow. This is armel. armhf is an
attempt to sort this all out and pass floating-point parameters in
actual floating-point registers, which apparently can get you a 40%
speed improvement.

I don't know how if this will realistically affect Lua --- it's pretty
float-heavy, but people tend not to do number crunching in it. And
LuaJIT ignores the ABI anyway and does its own thing, so... *shrug*

(I've seen claims that the Pi, in terms of pure CPU ability, is roughly
equivalent to a 300MHz PC. That doesn't include the superb GPU, of course.)

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