2010/3/27 Ronan Paixão <ronanpai...@yahoo.com.br>:
> One question: will Pari 2.4 be here to stay?
> If so, then it's (eventually) inevitable that a port will have to be made.
> However, I'm not familiar with Pari's development, so I don't know if
> the new API is stable enough yet to justify a port.
We should definitely move to PARI 2.4. We haven't only because it is
indeed a monumental task. Perhaps I'll do the move, since I wrote
most of the Sage wrapper of PARI anyways, and surely porting is much
less work than writing the whole wrapper in the first place. If
anybody wants to help, please volunteer. For starters:
* What is the relevant trac ticket?
* Whoever tried last (Nick?), can they summarize some of the issues
they encountered.
It could be worth moving straight to the pari 2.4 series for Sage-5.0.
In case there is confusion, I had some long chats about Pari 2.4
versus 2.3 with Karim Belebas (lead Pari dev) last time I was in
Bordeaux. The Pari 2.4 series is the one anybody should use if they
can use it. It's meant to be solid for normal research applications.
The reason it is called "unstable" is because the C API is not stable,
i.e., the PARI devs reserve the right to change the C API from version
to version.
For a long time Sage used the "unstable" series of PARI, until there
was one stable release, when we got stuck with that.
-- William
>
> Ronan
>
> ________________________________
> De: Hamish Ivey-Law <hamish.ivey....@gmail.com>
> Para: sage-devel <sage-devel@googlegroups.com>
> Enviadas: Quarta-feira, 24 de Março de 2010 8:45:58
> Assunto: [sage-devel] Re: Bug: Elliptic Curve Point Counting
>
> Hi Robert,
>
> On Mar 23, 4:39 pm, Robert Campbell <rcamp...@umbc.edu> wrote:
>> There is a bug somewhere in the point counting code for elliptic
>> curves. Checked both on Linux/4.2.x and OSX-PowerPC/4.2.1. The bug
>> appears to be either in the PARI ellsea routine or in the SAGE
>> interface to it. With some more time I plan to look further and look
>> for an easy fix (unless someone else is already doing the work). The
>> problem shows up with moderate sized curves over prime fields - a good
>> example being the NIST p-384 cryptographic curve:
>>
>> sage: p384 = 2^384 - 2^128 - 2^96 + 2^32 -1
>> sage: b384 =
>> 0xB3312FA7E23EE7E4988E056BE3F82D19181D9C6EFE8141120314088F5013875AC656398D8A2ED19D2A85C8EDD3EC2AEF
>> sage: E = EllipticCurve(GF(p384),[-3,b384])
>> sage: E.cardinality()
>>
>> /Applications/sage/sage-4.2.1/local/lib/python2.6/site-packages/sage/
>> schemes/elliptic_curves/sea.pyc
>> in ellsea(E, p, early_abort)
>> 45 gp.eval('E = ellinit(%s*Mod(1,%s));'%(E,p))
>> 46 N = gp.eval("ellsea(E,%s,0,%s)"%(p,int(early_abort)))
>> 47 if N.find("*") != -1:
>> ---> 48 raise RuntimeError, "Error: '%s'"%N
>> 49 return Integer(N)
>>
>> RuntimeError: Error: ' *** vector: length (lg) overflow'
>
> I'm almost certain that this is a limitation in the PARI 2.3 series
> (which is what Sage uses) caused by the limited number of division
> polynomials. I ran into the same problem when generating curves over
> large prime fields, and the solution Bill Allombert (a Pari developer)
> and I came up with was to add David Kohel's database of division
> polynomials to PARI's SEAdata package. That work had to be done on
> the 2.4 development branch of PARI, which is somewhat unfortunate
> since upgrading the PARI version used by Sage would be a monumental
> task due to the fact that PARI 2.4 breaks backwards compatibility with
> 2.3.
>
> I suppose ideally Sage would have its own Cython version of SEA (Sage
> already includes David's division polynomial base as the package
> 'database_kohel-20060803'), but for now I think the only way you'll be
> able to do point counting over prime finite fields bigger than about
> 256 bits is to use the development version of PARI. I would be
> pleased to be proved wrong however!
>
> Regards,
> Hamish.
>
> --
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> ________________________________
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--
William Stein
Associate Professor of Mathematics
University of Washington
http://wstein.org
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