Bill Allombert on Wed, 03 Feb 2010 18:23:12 +0100

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Re: ellap hangs on a large-ish prime

On Mon, Feb 01, 2010 at 09:50:24PM -0400, Jeremy Porter wrote:
> Greetings,
> In iteratively computing values of ellap(E,P) for the curve E =
> ellinit([0,0,1,-1,0]) for primes P of increasing size, I noticed that when P
> = 2486152157 my iteration would hang. Primes in a similar range (i.e.,
> nextprime(P+1) = 2486152159) are computed in well under a second, however I
> left this value of P to compute overnight without result.
> I initially noticed this when using libpari in a C program, then confirmed
> it with the GP calculator. An example follows:
> E = ellinit([0,0,1,-1,0]);
> P = 2486152157;
> isprime(P)
> ellap(E, nextprime(P+1))
> ellap(E, P)

Hello Jeremy, 
This issue should be fixed in PARI 2.3.5 which will be released on Friday.
A prerelease is available at
for testing.

Thanks a lot to have reported this problem!