E.minimal_model() crashes with large coefficients.

[sagetrac-weigandt]

This code

E=EllipticCurve([4382696457564794691603442338788106497, 28, 3992, 16777216, 298])
E.minimal_model()

Spits out this error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "_sage_input_23.py", line 10, in <module>
    exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("RT1FbGxpcHRpY0N1cnZlKFs0MzgyNjk2NDU3NTY0Nzk0NjkxNjAzNDQyMzM4Nzg4MTA2NDk3LCAyOCwgMzk5MiwgMTY3NzcyMTYsIDI5OF0pCkUubWluaW1hbF9tb2RlbCgp"),globals())+"\\n"); execfile(os.path.abspath("___code___.py"))
  File "", line 1, in <module>
    
  File "/tmp/tmpQWTtgb/___code___.py", line 4, in <module>
    exec compile(u'E.minimal_model()
  File "", line 1, in <module>
    
  File "/sagenb/sage_install/sage-5.0-boxen-x86_64-Linux/local/lib/python2.7/site-packages/sage/schemes/elliptic_curves/ell_rational_field.py", line 2552, in minimal_model
    F = self.pari_mincurve()
  File "/sagenb/sage_install/sage-5.0-boxen-x86_64-Linux/local/lib/python2.7/site-packages/sage/schemes/elliptic_curves/ell_rational_field.py", line 713, in pari_mincurve
    e = self.pari_curve(prec)
  File "/sagenb/sage_install/sage-5.0-boxen-x86_64-Linux/local/lib/python2.7/site-packages/sage/schemes/elliptic_curves/ell_rational_field.py", line 664, in pari_curve
    self._pari_curve[prec] = pari(list(self.a_invariants())).ellinit(precision=prec)
  File "gen.pyx", line 10416, in sage.libs.pari.gen._pari_trap (sage/libs/pari/gen.c:49843)
sage.libs.pari.gen.PariError: precision too low (10)

It looks like the precision needs to be increased when such a large curve is fed to PARI's minimal model algorithm.

Component: elliptic curves

Keywords: minimal model

Author: Jeroen Demeyer

Branch/Commit: u/jdemeyer/ticket/13163 @ 6092e94

Reviewer: John Cremona

Issue created by migration from https://trac.sagemath.org/ticket/13163

[jdemeyer]

Branch: u/jdemeyer/ticket/13163

[jdemeyer]

New commits:

6092e94

Increase precision if needed in E.pari_curve()

[jdemeyer]

Commit: 6092e94

[jdemeyer]

Author: Jeroen Demeyer

[JohnCremona]

comment:4

I think I might have been the person who first implemented the variable precision for pari curve construction, and did not do a perfect job. This looks pretty good to me.

[JohnCremona]

Reviewer: John Cremona