#18663: Speed up computation of twists of newforms
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Reporter: davidloeffler | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.8
Component: modular forms | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/davidloeffler/better_twists_2 | a99880cbde7ddefa6982e9c5b8ffb2565c5bc354
Dependencies: #18478 | Stopgaps:
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Changes (by davidloeffler):
* commit: 91d4941180104d20e3633ff0002295725de56db9 =>
a99880cbde7ddefa6982e9c5b8ffb2565c5bc354
Comment:
Here's a new version. I've made a subtle change which ensures that the
code cannot return bogus results (even if {{{check=False}}}); it now
either returns a correct answer, or fails with a {{{ValueError}}} if the
form is not new at the specified level. The change is that the code starts
by taking the new subspace of the modular symbols (which is pretty cheap
to compute) and only then starts filtering down to kernels of Hecke
operators.
I've also changed the error messages a bit so it returns a different error
if the computed mod sym space is 0 than if it's too large (the latter
could, theoretically, happen in valid examples if the level was gigantic,
whereas the former can only occur if the input is bogus so it makes sense
to return {{{ValueError}}}).
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New commits:
||[http://git.sagemath.org/sage.git/commit/?id=a99880cbde7ddefa6982e9c5b8ffb2565c5bc354
a99880c]||{{{Trac 18663: Speed up computation of twists of newforms}}}||
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Ticket URL: <http://trac.sagemath.org/ticket/18663#comment:9>
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