#11115: Rewrite cached_method in Cython
---------------------------+------------------------------------------------
Reporter: SimonKing | Owner: jason
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-4.7
Component: misc | Keywords: category cython cache
Work_issues: | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies:
---------------------------+------------------------------------------------
Comment(by SimonKing):
It occured to me that I did not yet provide an example to show cached
methods for elements that do not allow attribute assignment:
{{{
sage: cython("""from sage.structure.element cimport Element
cdef class MyElement(Element):
cdef object x
def __init__(self,P,x):
self.x=x
Element.__init__(self,P)
def __neg__(self):
return MyElement(self.parent(),-self.x)
def _repr_(self):
return '<%s>'%self.x
def raw_test(self):
return -self
""")
sage: class MyCategory(Category):
@cached_method
def super_categories(self):
return [Objects()]
class ElementMethods:
@cached_method
def test_cache(self):
return -self
sage: class MyParent(Parent): pass
sage: C = MyCategory()
sage: P = MyParent(category=C)
sage: e = MyElement(P,5)
sage: e
<5>
sage: -e
<-5>
# This is inherited from the category, ...
sage: e.test_cache()
<-5>
# ... and the cache works, ...
sage: e.test_cache() is e.test_cache()
True
# ... even though you can't set attributes:
sage: e.bla = 1
Traceback (most recent call last):
...
AttributeError:
'_mnt_local_king__sage_temp_mpc622_25602_tmp_1_spyx_0.MyElement' object
has no attribute 'bla'
# By lack of "setattr", the cache is not as fast as it could be, ...
sage: timeit('e.test_cache()')
625 loops, best of 3: 1.62 µs per loop
# ... but it is faster than to create a new element
sage: timeit('e.raw_test()')
625 loops, best of 3: 1.78 µs per loop
}}}
At sage-devel, Martin Raum suggested to time element creation (if I
understood his suggestion correctly).
I found without patch:
{{{
sage: K = GF(101)
sage: get_memory_usage()
839.96484375
sage: %time for i in xrange(10^7): a = K(i)
CPU times: user 25.19 s, sys: 0.01 s, total: 25.21 s
Wall time: 25.20 s
sage: get_memory_usage()
839.96484375
}}}
and with patch
{{{
sage: K = GF(101)
sage: get_memory_usage()
841.96875
# show that the new attribute is there, but it is non-initialized
sage: a=K(4)
sage: print a.__cached_methods
None
sage: %time for i in xrange(10^7): a = K(i)
CPU times: user 24.46 s, sys: 0.00 s, total: 24.46 s
Wall time: 24.46 s
sage: get_memory_usage()
841.96875
}}}
So the time actually improved with the patch, and the memory usage at
starting sage increased by as much as 0.24% - I hope that can be afforded.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11115#comment:24>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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