Sorry to bother you again, but I think that changes on a very basic
level such as sage/structure/element.pxd require sage-devel's
blessing.
On 25 Apr., 19:57, Simon King <simon.k...@uni-jena.de> wrote:
> The background of my question is trac ticket #11115. It provides a
> Cython version of @cached_method, and it is really fast now.
To back my claim up: With the patch, I obtain
sage: class MyClass:
....: def __init__(self):
....: self._cache = {}
....: @cached_method
....: def noarg_cache(self):
....: return True
....: def noarg(self):
....: return True
....: @cached_method
....: def arg_cache(self,x,n=10):
....: return x^n
....: def arg(self,x,n=10):
....: try:
....: return self._cache[x,n]
....: except KeyError:
....: a = self._cache[x,n] = x^n
....: return a
....:
sage: O = MyClass()
sage: timeit('O.noarg_cache()', number=10^6)
1000000 loops, best of 3: 104 ns per loop
sage: timeit('O.noarg()', number=10^6)
1000000 loops, best of 3: 237 ns per loop
sage: timeit('O.arg_cache(3)', number=10^6)
1000000 loops, best of 3: 942 ns per loop
sage: timeit('O.arg(3)', number=10^6)
1000000 loops, best of 3: 844 ns per loop
sage: timeit('O.arg_cache(3,10)', number=10^6)
1000000 loops, best of 3: 933 ns per loop
sage: timeit('O.arg(3,10)', number=10^6)
1000000 loops, best of 3: 1.01 µs per loop
So, if there are no arguments then the @cached_method is actually
faster than simply returning "True". With arguments, it can compete
with a self-made cache written in Python. But of course, using
@cached_method is more convenient than a hand-knitted cache.
Now, the proposed additional attribute is not related with the speedup
in the example above. But it would play a role if you have
* a cdef class derived from Element
* that does not allow attribute assignment and
* that inherits a cached method from the category framework.
Namely, the additional attribute makes the cache work in the situation
above.
One could argue:
1) The situation above is very rare, and if a developer wants that it
works for a cdef class Foo(Element), then s/he can still provide Foo
with a "cdef public dict __cached_methods": It is not needed to do
that on the level of sage.structure.element.
or
2) I worked with that patch, and I did not see memory problems. So,
apparently the additional attribute is lightweight enough. Thus we can
afford to make the creation of cached methods via categories as
convenient as possible.
I am in favour of 2).
Cheers,
Simon
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