#18979: avoid Maxima on creation of symbolic matrices
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Reporter: rws | Owner:
Type: | Status: needs_review
defect | Milestone: sage-6.9
Priority: major | Resolution:
Component: | Merged in:
linear algebra | Reviewers:
Keywords: | Work issues:
Authors: Ralf | Commit:
Stephan | 2c4fa619863baebcfe5239a2b325eabac83ed819
Report Upstream: N/A | Stopgaps:
Branch: |
u/rws/18979 |
Dependencies: |
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Comment (by nbruin):
I think invading a fundamental piece of infrastructure with specific tests
for a specific ring should not be taken lightly. I think you can avoid
most of your trouble by delaying the is_zero test to the last possible
moment:
{{{
elif self._nrows == self._ncols:
self._entries = [entries if i==j else zero for i in
range(self.nrows) for j in range(self.nrows)]
elif entries == zero:
self._entries = [zero]*(self._nrows*self._ncols)
else:
raise TypeError("nonzero scalar matrix must be square")
}}}
The first list comprehension can be optimized further, if required (I
suspect that testing whether "entries" is zero to more quickly create a
square zero matrix is a false optimization: if you need that thing quickly
often, you should reuse an immutable zero matrix. That will be much
quicker (and constant in size of the matrix!), so I don't think it's
necessary).
If the zero check is expensive, it will almost certainly lead to an error.
--
Ticket URL: <http://trac.sagemath.org/ticket/18979#comment:13>
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