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Sage 3.2.2: speed regression/infinite loop for "K.<b> = QQ[a]" #5338
Comments
comment:1
You can still access my old (numeric) minpoly code via
However, for many cases this is much slower or fails completely. |
comment:2
Hmm, this is insanely slow (i.e. never finishes for me)
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comment:3
Note that for now the doctest has been disabled to get the doctests to pass. Cheers, Michael |
comment:5
Replying to @robertwb:
The problem seems to be here:
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comment:6
Replying to @aghitza:
As far as I can see, the latter is getting into an infinite loop. If that is right, it's real bug and not just a new inefficiency. |
comment:7
It seems that
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comment:8
I've attached a patch that reverses the order: it first tries the numerical algorithm, and if that fails, it then tries the algebraic algorithm. This makes vastly more sense to me, since the numerical algorithm -- if it will fail -- is likely to fail in a reasonable amount of time, but the algebraic algorithm can succeed and take a huge amount of time. |
comment:9
We need to wrap raising this error to not be raised if the algorithm is numeric... I remember doing it in this order because there were cases where the numeric algorithm was way slower, but at least the numeric one finishes in constant bounded time. I really feel there should be a quicker way of computing compositums than using QQbar. |
comment:10
Attachment: trac_5338.2.patch.gz |
Author: William Stein |
Merged: sage-4.3.alpha1 |
Reviewer: Robert Bradshaw |
The code below works instantly in Sage 3.2.1, but starting with Sage 3.2.2 it doesn't even finish the last command in 30 minutes CPU time:
Carl Witty suggests:
This is likely related to the new embedding code in Sage 3.2.2, so I am CCing RobertWB.
Cheers,
Michael
CC: @robertwb
Component: algebra
Author: William Stein
Reviewer: Robert Bradshaw
Merged: sage-4.3.alpha1
Issue created by migration from https://trac.sagemath.org/ticket/5338
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