RE: [GD-Consoles] question: Embedded scripting language on consol e

[Tom F. <to...@mu...>]

Bear in mind that the project is only about a third of the way through, so
we haven't hit any evil crunch times yet.

Porting was pretty simple. You need to override the memory handling stuff to
use your own heaps of course, but that was pretty simple.

You also probably want to give Python its own heap because it does a lot of
12-byte allocations, and if you throw that in the general heap you'll get
horrible fragmentation. We used a stack-based allocator hard-coded to
deliver 12-byte entries - nice and fast, no fragmentation.

Biggest worry is speed on the PS2, because its cache is sooo tiny. But
Python is hardly a speed demon in the best of times, so you need to make
sure you're not using a "heartbeat" system (i.e. calling each object each
frame) - you need a queue-based event system and a C "autonomic" system to
do the mundane work. This is just good programming practice, whatever
language you use, but it's especially important when using a slow scripting
language for your high-level stuff.

SWIG takes a bit of work to integrate into the toolchain, and it's still not
great - it doesn't auto-SWIG headers very well, and we do tend to have to
manually do a "SWIG rebuild" quite often. However, it is pretty fast, so
that's not a big problem, it's just a bit annoying. I suspect we could fix
it easily if we just wrote a makefile (rather than trying to use VC.net's
stuff, which isn't very suited to this sort of stuff).

Benefits are that Python is incredibly easy to code, and we've got some good
stuff up and working very quickly. And of course you get a scripting
language that the designers can use "for free".

Yes, it's a brave step. But we know that if it does all fall down around our
ears and speed is a big problem, we can just port the code back to C, and
only use Python for actual "level scripts" (this switch opens this door,
stuff like that). SWIG is probably the most important bit of the puzzle,
because it means that you can freely mix and match Python and C - they can
access each others members and fucntions quite happily, which means you can
throw code from one to the other in case of speed emergencies. But we've not
had to so far.

Even if the worst happens and no trace of Python survives to the shipped
game (which I very very much doubt), Python is a great prototyping tool.

We were inspired by Humungous's work with Python and SWIG - they've
definately had more experience with this sort of stuff. IIRC, there's a GDC
talk they did on the pros and cons and gotchas. Definately worth checking
out.


Tom Forsyth - Muckyfoot bloke and Microsoft MVP.

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> -----Original Message-----
> From: Andrew Perella [mailto:aj...@eu...]
> Sent: 20 February 2003 10:54
> To: gam...@li...
> Subject: RE: [GD-Consoles] question: Embedded scripting language on
> console
> 
> 
> Hi Tom,
> 	Can you tell us more of your experiences with using 
> python on ps2/xbox/gc?
> What problems have you had? What unexpected benefits did you get? What
> worries do you have at the back of your mind? My feeling is 
> that this was a
> brave step to make at this time.
> Regards,
> Andrew
> 
> 
> Dr Andrew Perella
> Programming Manager
> aj...@eu...
> 
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