Problem with ellap

[Roland Dreier <droland@mail.math.okstate.edu>]

The default algorithm used by ellap appears to produce incorrect results.
(The curve below is not supersingular at 5, so we know right off the bat
that 0 must be wrong).

Roland

                       GP/PARI CALCULATOR Version 2.0.11 (beta)
                    i586 running linux (ix86 kernel) 32-bit version
                      (readline enabled, extended help available)

                              Copyright (C) 1989-1998 by
              C. Batut, K. Belabas, D. Bernardi, H. Cohen and M. Olivier.

Send bug reports, suggestions and patches to pari@math.u-bordeaux.fr
Type ? for help.

   realprecision = 28 significant digits
   seriesprecision = 16 significant terms
   format = g0.28

parisize = 20000000, primelimit = 500000, buffersize = 30000
? e = ellinit([0, 2, 0, 1, 1] * Mod(1, 5))
%1 = [Mod(0, 5), Mod(2, 5), Mod(0, 5), Mod(1, 5), Mod(1, 5), Mod(3, 5),
Mod(2, 5), Mod(4, 5), Mod(2, 5), Mod(1, 5), Mod(0, 5), Mod(2, 5), Mod(3,
5), 0, 0, 0, 0, 0, 0]
? ellap(e, 5)
%2 = 0
? ellap(e, 5, 1)
%3 = -4