#18269: A new structure for experimentation on decoding: communication channels
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Reporter: | Owner:
dlucas | Status: needs_work
Type: | Milestone: sage-6.7
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
coding theory | Work issues:
Keywords: | Commit:
Authors: | 5f31c5cef52b9b0bdbd905f4ff132e344446e766
Report Upstream: N/A | Stopgaps:
Branch: |
u/dlucas/channels |
Dependencies: |
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Comment (by vdelecroix):
> 13. I would rather implement `StaticErrorRateChannel.transmit_unsafe` as
> {{{
> def transmit_unsafe(self, msg):
> w = msg.copy()
> V = self.input_space()
> for i in sample_range(V.dim(), randint(*self.nb_errors())):
> w[i] = V.random_element()
> return w
> }}}
> it would be more direct. Moreover it shows that `sample_range` would
better be an iterator instead of returning a list. By the way, this
function `sample_range` has currently linear complexity in `n`, isn't it
possible to make it linear in `k`?
Yes it is (the solution is not exactly linear though)
{{{
sage: S = Subsets(100,4)
sage: timeit("S.random_element()")
625 loops, best of 3: 54.2 µs per loop
sage: timeit("sample_range(100,4)")
625 loops, best of 3: 57.7 µs per loop
sage: S = Subsets(1000,4)
sage: timeit("S.random_element()")
625 loops, best of 3: 61.2 µs per loop
sage: timeit("sample_range(1000,4)")
625 loops, best of 3: 510 µs per loop
}}}
It is roughly the same speed for `n=100` but for `n=1000` yours is twice
slower.
--
Ticket URL: <http://trac.sagemath.org/ticket/18269#comment:12>
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