Re: slow factor

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Wed, May 04, 2022 at 05:16:11PM +0800, Zhao Li wrote:
> Dear Bill,
> 
> 	Thank you. 
> 	In practice we can restrict the input polynomial in the integer ring.
> 	This function works very well. But we found it failed for this polynomial.
> 
> P = -400000*ieta + 3600000*ep*ieta + 4*ep*ieta^2 - 11300000*ep^2*ieta - 20*ep^2*ieta^2 + 15000000*ep^3*ieta + 33*ep^3*ieta^2 - 7200000*ep^4*ieta - 18*ep^4*ieta^2;

What is the problem ? It works for me:

? factorback(factor(P))==-P
%2 = 1
? factorback(fact(P))==-P
%3 = 1

Maybe the issue is that P has square factors:

? fact(P)
%4 = [ieta,1;2*ep-1,1;3*ep-2,2;(ieta+400000)*ep-100000,1]

Cheers,
Bill.