qfrep

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

Dear pari-dev,

  I have applied a patch by Gonzalo Tornaria implementing a new routine

   qfrep(q, B, {flag = 0}):

   q  being  a  square and symmetric matrix with integer entries representing a
positive definite quadratic form,  outputs the vector whose i-th entry,  1 <= i
<= B is half the number of vectors v such that q(v)  = i.   This routine uses a
naive  algorithm  based  on qfminim,  and will fail if any entry becomes larger
than 2^{31}.

   The binary digits of flag mean:

   * 1: count vectors of even norm from 1 to 2B.

   * 2: return a t_VECSMALL instead of a t_GEN

   The library syntax is qfrep0(q, B, flag).


Gonzalo needed it to identify the associated theta series, and it's rather
less cumbersome than calling qfminim, storing all the minimal vectors and
sorting the result by increasing norm.

'rep' stands for "representation". Does anybody see a better name ?

Cheers,

    Karim.
-- 
Karim Belabas                     Tel: (+33) (0)1 69 15 57 48
Dép. de Mathématiques, Bât. 425   Fax: (+33) (0)1 69 15 60 19
Université Paris-Sud              http://www.math.u-psud.fr/~belabas/
F-91405 Orsay (France)            http://pari.math.u-bordeaux.fr/  [PARI/GP]