#14214: Cythoned homsets
----------------------------------------------+-----------------------------
Reporter: SimonKing | Owner: tbd
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.10
Component: performance | Resolution:
Keywords: Hom, cython, cached method | Work issues: How to store
domain and codomain?
Report Upstream: N/A | Reviewers:
Authors: Simon King | Merged in:
Dependencies: #14159, #12951, #13184 | Stopgaps:
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Comment (by SimonKing):
My frustration level raises.
Ideally, one would write a descriptor
- that takes the value from `__cached_methods`, because this is much
faster than relying on `__getattr__` (which looks into `__cached_methods`
as well)
- that can be overridden on the instance's `__dict__`, because python
attribute access is faster than accessing the property, and in addition
the property access tends to get slower on sub-classes.
Didn't you say that a property that only defines `__get__` can be
overridden in the instance's dict? So, I thought I just define `__get__`
and not set, and put data into `__dict__` when possible.
However, it does not work:
{{{
sage: cython("""
....: from sage.all import Sets
....: from sage.structure.parent cimport Parent
....: cdef class Bla(Parent):
....: def __init__(self, D,C):
....: try:
....: self.__dict__['_domain'] = D
....: self.__dict__['_codomain'] = C
....: except AttributeError:
....: if self.__cached_methods is None:
....: self.__cached_methods = {'_domain':D, '_codomain':C}
....: else:
....: self.__cached_methods['_domain'] = D
....: self.__cached_methods['_codomain'] = C
....: Parent.__init__(self, category = Sets())
....: property _domain:
....: def __get__(self):
....: try:
....: return self.__cached_methods['_domain']
....: except KeyError:
....: raise AttributeError("%s instance has no attribute
'_domain'"%type(self))
....: """)
....:
sage: class Blubb(Bla): pass
sage: b = Bla(1,2)
sage: c = Blubb(1,2)
sage: b._domain
1
sage: c._domain
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
<ipython-input-19-9505626a8e7d> in <module>()
----> 1 c._domain
/home/simon/SAGE/prerelease/sage-5.9.rc0/local/lib/python2.7/site-
packages/sage/structure/parent.so in
sage.structure.parent.Parent.__getattr__ (sage/structure/parent.c:6501)()
/home/simon/SAGE/prerelease/sage-5.9.rc0/local/lib/python2.7/site-
packages/sage/structure/misc.so in
sage.structure.misc.getattr_from_other_class
(sage/structure/misc.c:1591)()
AttributeError: 'Blubb_with_category' object has no attribute '_domain'
sage: c.__dict__['_domain']
1
}}}
So, can you please clarify: What kind of descriptors can be overridden in
`__dict__`?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14214#comment:38>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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