#13304: Very inefficient scalar multiplication on FreeModule_ambient with
somewhat
large rank
------------------------------+---------------------------------------------
Reporter: daniels | Owner: daniels
Type: defect | Status: new
Priority: minor | Milestone: sage-5.3
Component: linear algebra | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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As reported in a [https://groups.google.com/d/topic/sage-support/jlLTyY-
8H8c/discussion thread in sage-support] trivial scalar multiplication in
`FreeModule_ambient` can be extremely slow or lead to out of memory
errors:
{{{
n = 10000
v = vector([0]*n) # ok so far
v2 = v/1 # kaboom
}}}
The problem is that, during coercion, `_an_element_impl()` and in turn
`gen(0)` of `FreeModule_ambient` gets called. The default implementation
of `gen` calls `basis()`, computing the entire standard basis, and then
returns the first basis vector.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13304>
Sage <http://www.sagemath.org>
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