#14054: Cythoned UniqueRepresentation
-----------------------------------------------+----------------------------
Reporter: SimonKing | Owner: tbd
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.7
Component: performance | Resolution:
Keywords: cython UniqueRepresentation | Work issues:
Report Upstream: N/A | Reviewers: Travis
Scrimshaw
Authors: Simon King | Merged in:
Dependencies: #14017 | Stopgaps:
-----------------------------------------------+----------------------------
Old description:
> `UniqueRepresentation` provides a comfortable way to create unique parent
> structures, and automatically provides a hash and certain comparison
> methods. Problem: It relies on a metaclass, namely `ClasscallMetaclass`
> and thus has to be a Python class. That's bad for speed.
>
> Here, I suggest to create a new cdef class `UniqueRepresentation_c` that
> provides hash and comparison, and let `UniqueRepresentation` inherit from
> it, just adding the classcall method.
>
> The problem is that `UniqueRepresentation` relies on cached_method, and
> this decorator had problems to work on methods defined in Cython with
> varargs and keywords arguments. That is fixed in #14017, which is thus a
> dependency.
New description:
`UniqueRepresentation` provides a comfortable way to create unique parent
structures, and automatically provides a hash and certain comparison
methods.
Problems:
- It relies on a metaclass, namely `ClasscallMetaclass` and thus has to be
a Python class. That's bad for speed.
- It combines two features, namely a cache and unique instance behaviour.
But in many some cases we want a cache so that two distinct instances can
still be equal.
Here, I suggest to
1. separate the two features, by creating a new class
`sage.unique_representation.CachedRepresentation` as one base of
`UniqueRepresentation`.
2. create a new cdef class `sage.misc.fast_methods.WithRichCmpById`, that
provides hash and rich comparison, as expected for unique instance
behaviour.
__Apply__
- [attachment:trac14054_fast_methods.patch]
--
Comment (by SimonKing):
The patch should now be ready for review.
Two questions that I'd like to have addressed:
1. I introduce `provide_hash_by_id`, but I don't use it. Shall it be
deleted?
2. Is it enough to override the rich comparison methods? Currently, one
can have `hash(a)!=hash(b)` but `cmp(a,b)==0`. Does this violate the
contract of hash functions? Or is it enough that `hash(a)!=hash(b)`
implies `a!=b`?
Pathbot:
Apply trac14054_fast_methods.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14054#comment:12>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac?hl=en.
For more options, visit https://groups.google.com/groups/opt_out.
