#20287: Implement the Moore–Penrose matrix pseudoinverse
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Reporter: jdemeyer | Owner:
Type: enhancement | Status: positive_review
Priority: major | Milestone: sage-7.2
Component: linear algebra | Resolution:
Keywords: | Merged in:
Authors: Jeroen Demeyer | Reviewers: Frédéric Chapoton
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/jdemeyer/pseudoinverse | 3a3f5521eb8ced6c64a329918ac3544633286e89
Dependencies: #20286 | Stopgaps:
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Comment (by mjo):
Replying to [comment:16 jdemeyer]:
> General principle: because I see no reason to ''not'' offer the choice.
If a choice is available, why not allow the user to override that choice?
Of course, offer a good default.
I generally agree, but I wanted to be sure that the choice we're giving
the user isn't `do_it_wrong=True`. If the default always does the right
thing, and one of the other algorithms might not, then it's just noise in
the docstring. And we'd have to go through a deprecation cycle to change
it in the future.
> I disagree completely. This has nothing to do with the `type()` of the
matrix, but with the mathematical properties of the parent.
Fair enough, but the resulting type of the matrix is determined by the
ring that you pass in (and whether or not it's sparse).
> With your proposal, `pseudoinverse()` would no longer work for matrices
over `RR` or `CC` or for sparse matrices.
You would at least get the exact(conj) implementation in every case. But
you would have to override that in every subclass where it makes sense,
like the generic_dense ones for RR/CC. If that's difficult or results in
code duplication, then it's fine as-is. I just brought it up in case you
hadn't considered it.
--
Ticket URL: <http://trac.sagemath.org/ticket/20287#comment:17>
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