Re: Slow polynomial division?

[Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr>]

On Wed, Jun 26, 2013 at 10:41:55AM +0100, Richard in Reading wrote:
> ? allocatemem(2^33)
>   ***   Warning: new stack size = 8589934592 (8192.000 Mbytes).
> ? e=ellinit("69696bf1");
> ? f=elldivpol(e,11*15)/elldivpol(e,55);
> 
> The divisor has a degree and coefficients with digit-length around 1500 and
> the dividend has degree and coefficient-digit-length around 15000. After
> running for 111 hours the division seemed not to have completed. 
> 
> Calculating the polynomials themselves seems to take a minute or so.
> 
> Is this expected?

Not really. The division only takes 12 minutes on paridev (with both 2.6.1 and 2.5.4).

I suggest you use \ instead of / since you know the result is a polynomial.
f=elldivpol(e,11*15)\elldivpol(e,55);

Cheers,
Bill.