#12141: Implement finite algebras
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Reporter: johanbosman | Owner: AlexGhitza
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.2
Component: algebra | Resolution:
Keywords: sd51 | Merged in:
Authors: Johan Bosman, | Reviewers:
Peter Bruin, Michiel Kosters | Work issues:
Report Upstream: N/A | Commit:
Branch: | 42e2f4ef1a2a86864c0e5f08e7c247763842a553
public/algebras/finite_algebras-12141| Stopgaps:
Dependencies: |
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Comment (by tscrim):
Hey Peter,
Replying to [comment:25 pbruin]:
> I haven't had the time to review your changes in detail, but here are a
few things I noticed:
> - you changed "EXAMPLE::" to "EXAMPLES::" in many places where there is
only one example; do you have a reason for this?
As I understand it, `EXAMPLES::` (and `TESTS::`) is the standard idiom,
not the singular version even if there is only one such example. Although
I seem to have missed some that I should also change to be consistent,
unless you feel that I should change them back (I don't hold a strong
opinion on this).
> - I think it should be "finite-dimensional algebra", not "finite
dimensional algebra", since "finite-dimensional" is used as a single
adjective.
Will change.
> - Are you sure that the inverse of an element should be cached? This
looks like it could waste a lot of memory. My impression is that in
general only properties of parents should be cached. If any inverse
should be cached at all, why not just that of the underlying matrix?
It depends. Things that are very memory/computationally intensive to
compute but not to store are candidates for a cache, especially when it's
likely to be a bottleneck.
Also it's not using much more memory by caching the element as opposed to
the matrix (nor does it generate a memory leak). So let's say `x^-1 = y`,
then `x` has `y` stored in its cache. So once you delete `x`, you also
delete the cache containing `y`. Perhaps what we should do is have a
`@lazy_attribute` called `_inverse` which will point to `y`, and then if
we construct `x^-1`, we can set `y._inverse = x`.
The other option if you're worried about memory usage is to make it a
`@weak_cached_function`, which allows it to be garbage collected if there
is no strong reference to `x^-1` and memory is needed elsewhere.
--
Ticket URL: <http://trac.sagemath.org/ticket/12141#comment:26>
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