Changes between Initial Version and Version 1 of Ticket #13714


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Timestamp:
12/28/12 08:11:52 (7 years ago)
Author:
Bouillaguet
Comment:

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  • Ticket #13714 – Description

    initial v1  
    1 On sage 5.4:
     1On sage 5.5:
    22{{{
    33sage: R.<x1,x2> = QQ[]
    44sage: I = R.ideal(x2**2 + x1 - 2, x1**2 - 1)
    55sage: R.one().lift(I)
    6 [0, 0]
     6Traceback (most recent call last):
     7...
     8ValueError: polynomial is not in the ideal
     9}}}
     10And then the bug:
     11{{{
    712sage: I.complete_primary_decomposition()
    813// ** char_series returns 0 x 0 matrix from 3 input polys (0)
     
    1015I[1,2]=x1^2-1
    1116}}}
    12 and hangs forever (on sage 5.3 it just SEGFAULTs).
     17and hangs forever (on sage 5.3 it just SEGFAULTed).
    1318
    14 The key in this case is the '''failing''' call to {{{lift}}}, ''i.e.'', evaluating {{{f.lift(I)}}} while `f` is not in `I`. What happens in these case is changed by #13671 (but the problem in this ticket is independent). It was found while fixing #13671 that when computing {{{f.lift(I)}}}, then if `f` is not in `I` an error is raised by singular, by setting a global variable. Before #13671, this variable was not reset, and subsequent calls to lift would return junk. After #13671, the global variable is reset and ``lift`` works correctly. However, it was apparently not the end of the story.
     19The key in this case is the '''failing''' call to {{{lift}}}, ''i.e.'', evaluating {{{f.lift(I)}}} while `f` is not in `I`. What happens in this case has been changed by #13671 (but the problem in this ticket is independent). It was found while fixing #13671 that when computing {{{f.lift(I)}}}, then if `f` is not in `I` an error is raised by singular, by setting a global variable. Before #13671, this variable was not reset, and subsequent calls to {{{lift}}} would return junk. After #13671, the global variable is reset and {{{lift}}} works correctly. However, it was apparently not the end of the story.