[john.cremona@gmail.com: Sage & Pari]

[Karim Belabas <Karim.Belabas@math.u-bordeaux1.fr>]

----- Forwarded message from John Cremona <john.cremona@gmail.com> -----

Date: Mon, 25 Jul 2011 14:40:40 +0100
From: John Cremona <john.cremona@gmail.com>
To: SAGE devel <sage-devel@googlegroups.com>
Cc: Karim Belabas <Karim.Belabas@math.u-bordeaux1.fr>
Subject: Sage & Pari

I had an interesting conversation with Karim Belabas, lead developer
of the Pari project (which Sage relies on for many things, including
most number field functionality).  I specifically asked him how he saw
the Sage/Pari relationship.  I have CC'ed him to this email, and hope
that if there is anything I have forgotten (we were eating lunch and I
did not take notes!) he will come forward.

Here is a specific thing:  he has noticed that the number of citations
(or just mentions) to the use of Pari/GP in mathematical papers has
been declining recently.  References to Sage have been increasing.  It
is quite possible that there are people who used to use Pari/GP
directly but now use Sage as an interface to it, possibly without
realising that they are still using Pari/GP.  It is not a new problem
that Sage users can easily omit to credit the authors of components of
Sage in their papers, and we should perhaps redouble our efforts to
make it easier for this not to happen.

Ironically, one reason why Pari is especially keen to get credit for
itself right now is that after years of having essentially zero
funding, at the moment Pari is enjoying the opposite situation, with
money for people as well as machines;  and this makes it particularly
important for them to be able to point to how much their package is
used.  Sage developers will understand this!

A second point Karim made is that he would like to see more more cases
(currently: 0)  in which a deficiency in a part of Pari used by Sage
-- for example, some number field functionality -- was fixed by
contributions to Pari itself, rather than by adding the extra
functionality within the Sage library.   [Example:  I use the
idealstar() function in Pari which gives the group structure and
generators for Z_K/I where I is an ideal in the ring of integers Z_K
of a number field K.  But I needed more, namely the same for the
quotient of this by units in Z_K.  So I (with Maite Aranes) wrote such
a function in Sage.  It turns out that Pari has such a function
internally, but exposed to users;  and if I had asked it would have
been possible to make it available.]

There were other issues, but that's all I remember right now.

John

----- End forwarded message -----

    K.B.
--
Karim Belabas, IMB (UMR 5251)  Tel: (+33) (0)5 40 00 26 17
Universite Bordeaux 1          Fax: (+33) (0)5 40 00 69 50
351, cours de la Liberation    http://www.math.u-bordeaux1.fr/~belabas/
F-33405 Talence (France)       http://pari.math.u-bordeaux1.fr/  [PARI/GP]
`