Speed: bytecode vz C API calls

[Stuart Bishop]

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On 10/12/2003, at 8:55 AM, Jacek Generowicz wrote:

> Peter Otten <__peter__ at web.de> writes:
>
>> Jacek Generowicz wrote:
>>
>>> aahz at pythoncraft.com (Aahz) writes:
>>>
>>>> I think you're going to need to write a solution that doesn't call
>>>> functions (function unrolling, so to speak).  Instead of returning a
>>>> memoizer function, just use a dict of dicts.
>>>
>>> Sounds interesting. But how do I get the dictionary to use the
>>> function which it is memoizing, to calculate values which haven't 
>>> been
>>> cached yet?
>>
>> Guessing into the blue:
>>
>> try:
>>     result = cache[fun, args]
>> except KeyError:
>>     result = cache[fun, args] = fun(args)
>
> Allow me to remind you of the memoizer I posted at the top of the 
> thread:
>
>   def memoize(callable):
>       cache = {}
>       def proxy(*args):
>           try: return cache[args]
>           except KeyError: return cache.setdefault(args, 
> callable(*args))
>       return proxy
>
> One key feature of this is that I can use it to replace any[*]
> function with a functionally equivalent but faster one, without having
> to change any of the call sites of the original.


> proxy does. However, it's the "almost" that creates the problem. If
> I'm prepared to mess around with the calls to the original functions
> and replace them with your suggestion, then, of course the problem is
> solved ... however, I _really_ do not want to replace the calls to the
> original ...

About the only thing that could be done then is:

def memoize(callable):
	cache = {}
	def proxy(*args, _cache=cache):
		try: return _cache[args]
		except KeyError: return cache.setdefault(args, callable(*args))
	return proxy

Might help a little bit, although probably not enough.

- --  
Stuart Bishop <stuart at stuartbishop.net>
http://www.stuartbishop.net/
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