[Python-ideas] functools.lru_cache manual cache modification

Constantin Berhard constantin at exxxtremesys.lu
Fri Dec 5 01:49:36 CET 2014

On 04.12.2014 15:02, Nick Coghlan wrote:
> As Ethan suggests, a clearer explanation of the current
> incompatibility, and what additional cache entries you would like to
> be able to inject may help us better understand the suggestion.

You're right. I'm sorry for being unclear.

I now have written code that compares
a) a stupid custom cache, which offers the interfaces I need ("f")
b) the most stupid way to combine libtco with lru_cache ("f2")
c) the slightly less stupid way to combine libtco with lru_cache ("f3")

A test run computes in this order: f(6), f(6), f(4)
in a) only the first computation has to be done, the other two are in
cache afterwards
in b) nothing can be cached
in c) only exact arguments can be cached, i.e. f(6) is only calculated
once, but the intermediate result that was calculated on the way is not
used to have f(4) in the cache, so f(4) has to be completely recomputed.

The code is here:
It's a single python 3 script ready for execution. These changes, when
properly split up will also find their way into the libtco git.

As you can see from the code, the interface I propose just adds two
functions to the cache: cache_get and cache_put. I think that any cache
should be able to provide these functions, no matter how its cache
strategy or how it is implemented.

I'm sorry if my code is tldr, but I really can't think of an easy way of
explaining it right now. I'll be happy to answer further questions though.

Best Regards,

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