Re: GP: algdep() bug?

[Michael Somos <somos@grail.cba.csuohio.edu>]

Okay, I missed the obvious again. The degree of the polynomial
should have been 32. It would have been 16 if complex integer
coefficients were allowed. My mistake. Thanks for the info.
I will try to remember in future. Shalom, Michael

On Wed, 8 May 2002, Bill Allombert wrote:

> On Sun, May 05, 2002 at 10:49:04PM -0400, Michael Somos wrote:
> > Pari Developers,
> > 
> > I don't know if this is exactly a bug, but perhaps there is some
> > other explanation why it won't find the polynomial :
> > 
> > ? p=x^8+1+9424*(-x^7+x^5+x^3-x)+7740*(x^6+x^2)+15494*x^4;
> > ? p2=subst(p,x,I*x^2);
> > ? rp2=polroots(p2);
> > ? r2_7=rp2[7];    
> > ? print(algdep(r2_7,16));
> >   ***   precision too low in lindep.
> > 
> > It seems to me that 4000 digits should be enough, but I have been
> > wrong before. Shalom, Michael
> 
> This means that there is no relations of degree less than 32, so
> algdep(r2_7,16) can't find anything. Increasing the precision make things
> "worse" since it reduce the chance that algdep find a false relation.
> (with \p9 you find x^5 - 1)
>