[GiNaC-list] factor() hangs on a simple expression, randomly

Richard B. Kreckel kreckel at in.terlu.de
Fri Dec 22 09:09:35 CET 2017

Hi Vitaly,

On 11/30/2017 05:16 PM, Vitaly Magerya wrote:
>     > factor((2*x-l)^2*(-1+6*x-l)*(-1+3*x-l)*(-2+4*x-l)*(1+4*x-l)*(4*x-l)*(2+4*x-l));
> At this point ginsh either hangs (80% of cases), or gives the correct
> result (20% of cases).


> So, any ideas on the nature of this problem, and how to fix it?

How did you find this polynomial which makes Hensel lifting keep
failing? How many of them are there?

Are they always multivariate? Do they always fail sometimes, work at
other times?

If the answer to the last two questions is yes, then we might add a stop
condition and when that has been reached, try factorizing with an
alternative permutation of symbols.

just an idea
Richard B. Kreckel

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