[Python-Dev] Optimization idea

Jack Jansen jack@oratrix.nl
Thu, 19 Aug 1999 16:06:01 +0200

I just had yet another idea for optimizing Python that looks so plausible that 
I guess someone else must have looked into it already (and, hence, probably 
rejected it:-):

We add to the type structure a "type identifier" number, a small integer for 
the common types (int=1, float=2, string=3, etc) and 0 for everything else.

When eval_code2 sees, for instance, a MULTIPLY operation it does something 
like the following:
	w = POP();
	v = POP();
	code = (BINARY_MULTIPLY << 8) |
		((v->ob_type->tp_typeid) << 4) |
	x = (binopfuncs[code])(v, w);
	.... etc ...

The idea is that all the 256 BINARY_MULTIPLY entries would be filled with 
PyNumber_Multiply, except for a few common cases. The int*int field could 
point straight to int_mul(), etc.

Assuming the common cases are really more common than the uncommon cases the 
fact that they jump straight out to the implementation function in stead of 
mucking around in PyNumber_Multiply and PyNumber_Coerce should easily offset 
the added overhead of shifts, ors and indexing.

Any thoughts?

Jack Jansen             | ++++ stop the execution of Mumia Abu-Jamal ++++
Jack.Jansen@oratrix.com | ++++ if you agree copy these lines to your sig ++++
www.oratrix.nl/~jack    | see http://www.xs4all.nl/~tank/spg-l/sigaction.htm