[chuck-dev] more on the 64-bit problem: hope?

M. Edward (Ed) Borasky znmeb at cesmail.net
Wed Aug 6 22:21:18 EDT 2008

On Wed, 2008-08-06 at 21:44 -0400, Stephen Sinclair wrote:

> By the way, this little excursion into the source made me notice that
> every single chuck instruction is executed as a virtual function.
> This means that for every instruction the struct must be dereferenced,
> and then it's vtable, and then the function can be called.  This would
> be a great place to look into for optimization, I think.  A jump table
> or big switch statement with inlined functions might be way faster.

1. Before you do any optimization, it might be worthwhile to do some
profiling. I don't happen to have a 32-bit machine handy (actually, I
have one but it's a laptop and probably way underpowered for ChucK.) But
I do have the "recipes" for profiling Linux code down to the chip level
(cache misses, pipeline stalls, close-enough-for-government-work
annotated source and assembler listings, etc.), courtesy of "oprofile". 

2. If you're digging down into virtual machines, "pseduo-instruction
dispatching", interpreters, etc., you should probably read
http://www.complang.tuwien.ac.at/forth/threaded-code.html. There's a
little "trick" you can use to speed up threaded code if you're willing
to use a non-standard feature of GCC that most compilers don't have, and
some other things you can do to speed up other forms of dispatch. 

M. Edward (Ed) Borasky

"A mathematician is a machine for turning coffee into theorems." --
Alfréd Rényi via Paul Erdős

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