#18979: avoid Maxima on creation of symbolic matrices
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Reporter: rws | Owner:
Type: defect | Status: needs_work
Priority: major | Milestone: sage-6.9
Component: linear algebra | Resolution:
Keywords: | Merged in:
Authors: Ralf Stephan | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/rws/avoid_maxima_on_creation_of_symbolic_matrices|
75e679c687019c9657188003306bbd08314919a5
Dependencies: | Stopgaps:
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Changes (by vdelecroix):
* status: needs_review => needs_work
Comment:
Hi,
I really do not like your solution. You are invading a generic class with
some specialized code. Moreover, the issue you found might be present in a
lot of other places. You should find a better way to do this test without
having to care whether the input is symbolic. If each ring needs a
specialized treatment it will become a complete nightmare.
Secondly, the operations `import XYZ` and `isinstance(x, my_type)` are not
at all negligeable. Though, in this case it is not very noticeable since
the cost is elsewhere. But with your strategy, you are potentially slowing
down everthing for a corner case speed up.
In this very particular case of matrices, there is a simpler way to fix
the issue. You can just avoid testing anything. In case `x` is zero a
useless filling will be done but of no harm (it is very quick compared to
the rest of the initialization). If you like better my solution, write at
least a comment that we should not test wheter the input is zero.
Vincent
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Ticket URL: <http://trac.sagemath.org/ticket/18979#comment:5>
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