Igor Schein on Fri, 7 Mar 2003 11:11:52 -0500


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Re: rnflllgram() regression


On Mon, Mar 03, 2003 at 12:48:04PM +0100, Karim BELABAS wrote:
> On Sun, 2 Mar 2003, Igor Schein wrote:
> > ? nf=nfinit(y^9-10*y^8-y^7+7*y^6+y^5-y^4+5*y^2+9*y+4);
> > ? pol=x^9-10*x^8-10*x^7+6*x^6-4*x^5+7*x^4+7*x^3+8*x^2-1;
> > ? rnflllgram(nf,pol,rnfpseudobasis(nf,pol));
> >   ***   not a definite matrix in lllgram
> >
> > It was broken some time between 2.2.4 and 2.2.5
> 
> Precision loss. It occured in 2.2.4 also, but was slightly less acute
> (different internal nf format), hence was hidden / disregarded [ and the
> result was incorrect: not LLL reduced ].
> 
> At \p50 it works.

Any way to have precision insufficiency detected?  I mean, the error
seems pretty arbitrary, even I didn't think to try higher precision,
and I should definitely know by now :)  

Thanks

Igor