#18979: avoid Maxima on creation of symbolic matrices
-------------------------------------+-------------------------------------
Reporter: rws | Owner:
Type: defect | Status: needs_review
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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Description changed by rws:
Old description:
> People have no idea what they ask for when they write `if ex != 0:` with
> `ex` possibly(!) a symbolic expression. E.g. this happens to trigger in
> `matrix/*` the full blown procedure of starting Maxima with its limited
> deductive armament trying to prove that `ex` is nonzero. This when all
> was wanted was that it not be a "numeric" zero.
>
> This ticket replaces the two instances in `matrix/` where such behaviour
> was triggered in doctests. Speedups are expected.
New description:
People have no idea what they ask for when they write `if ex != 0:` with
`ex` possibly(!) a symbolic expression. E.g. this happens to trigger in
`matrix/*` the full blown procedure of starting Maxima with its limited
deductive armament trying to prove that `ex` is nonzero. This when all was
wanted was that it not be a "numeric" zero.
This ticket replaces the two instances in `matrix/` where such behaviour
was triggered in doctests.
Compare on fresh Sage:
Before:
{{{
sage: %timeit M = matrix(SR, 2, 2, x^2 - 2*x + 1)
The slowest run took 468.13 times longer than the fastest. This could mean
that an intermediate result is being cached
1 loops, best of 3: 2.08 ms per loop
}}}
After:
{{{
sage: %timeit M = matrix(SR, 2, 2, x^2 - 2*x + 1)
The slowest run took 815.87 times longer than the fastest. This could mean
that an intermediate result is being cached
10000 loops, best of 3: 82.8 µs per loop
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/18979#comment:3>
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