#20693: Sage crashes when computing newforms
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Reporter: ehlen | Owner:
Type: defect | Status: new
Priority: critical | Milestone: sage-7.3
Component: modular forms | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by pbruin):
Replying to [comment:10 ehlen]:
> I did similar profiling tests as you did, @pbruin and discovered that
the main reason for this being slow is that elements in the base ring (a
cyclotomic field) get coerced into a relative extension (obtained by
adjoining the roots of a hecke polynomial). This is damn slow for some
reason (note that it is stated in the documentation of relative number
fields that doing arithmetic in number field towers is very slow but it
seems that it got worse than it used to be). I discovered that such
operations can be accelerated by very stupid means. For instance, instead
of coercing an element e of K into an extension L directly, write it in
terms of a power basis (e.list()), coerce the generator of K into L and
create the element corresponding to e in L directly. I can document some
examples later.
It turns out that `NumberField_relative.__base_inclusion()` uses a PARI
function that is too general (and hence too slow) for this purpose. I
opened #20749 to address this.
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Ticket URL: <http://trac.sagemath.org/ticket/20693#comment:13>
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