#18106: Maximum depth recursion in QQbar
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Reporter: vdelecroix | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.6
Component: number fields | Resolution:
Keywords: sd66 | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by vdelecroix):
Replying to [comment:2 gagern]:
> On the other hand, we could also try addressing the source of this deep
recursion. The way I see it, that's because addition is left associative,
so that cyclotomic polynomial will be a very deep but thin binary tree. If
we had a representation which describes a sum (and perhaps also a product)
of an arbitrary number of algebraic numbers using a single descriptor, the
data structure would become much more shallow.
Looks like a good idea to have a polynomial descriptor for one (or
several?) algebraic numbers. It might even be used to get faster and more
precise interval evaluations.
> As a third solution, we might set up our own evaluation machinery for
these trees, with our own stack instead of Python recursion. I haven't yet
worked out all the details, but if this sounds interesting I might write
some code to see how this approach feels.
Looks reasonable to do it without recursion. We might obtain a good speed
up.
> The way I see it, since the backtrace is about `_interval_fast` and
`_more_precision`, all of this is happening before exact computation is
triggered, right?
Right!
Do you find reasonable to open two tickets:
- one for polynomial descriptor in one variable
- one for evaluation without recursion
Vincent
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Ticket URL: <http://trac.sagemath.org/ticket/18106#comment:3>
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