Bug #1100
PrimaryDecomposition0: says not 0-dim but IsZeroDim says ideal is zero-dim!
Description
Bug summarized in this transcript
/**/ L:=[3*x^3*y +3*y*z^3 +1, 2*x*y*z^2 +3*x, 2*y^3*z +1];
/**/ I := ideal(L);
/**/ IsZeroDim(I);
true
/**/ PrimaryDecomposition0(I);
--> ERROR: IsPrimary: implemented only for 0-dimensional ideals
--> WHERE: at line 20 (column 5) of maximal.cpkg5
--> error("IsPrimary: implemented only for 0-dimensional ideals");
--> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
CONTEXT: function IsPrimary at line 20 of maximal.cpkg5
CALLED BY: function PrimaryDecomposition0 at line 38 of PrimaryDecomposition0.cpkg5
called at top-level
Related issues
History
#1
Updated by Anna Maria Bigatti over 6 years ago
Updated by - Assignee set to Anna Maria Bigatti
- % Done changed from 0 to 10
With SetVerbosity(90) it appears that down in the recursion it get an ideal=(1).
Investigating (should never happen!)
#2
Updated by Anna Maria Bigatti over 6 years ago
Found it: we knew it could happen, and this is the first time I see it!
The modular reconstruction gives the wrong minimal polynomial (may happen, of course).
That fact can be easily detected when one of the ideals I+ideal(factor) = 1.
In fact we never checked that the evaluation of the minpoly is in I!
I'll add this check to the code of MinPolyModular (this is in CoCoALib).
#3
Updated by Anna Maria Bigatti over 6 years ago
- Related to Bug #1101: Bug in MinPolyModular (insufficient rational reconstruction) added
#4
Updated by Anna Maria Bigatti over 6 years ago
- Status changed from New to Feedback
- % Done changed from 10 to 90
- Estimated time set to 1.01 h
Fixed: was a problem in MinPolyModular.
#5
Updated by John Abbott over 6 years ago
Updated by Anna: have you added the example(s) as a tests cases in the CoCoA test suite?
#6
Updated by John Abbott over 6 years ago
Here is a zero-dim ideal with primdecomp having 32 components:
I := ideal(x^4 +x^2 +1, y^4 +y, z^4 +z);
Might be useful sooner or later?
#7
Updated by Anna Maria Bigatti over 6 years ago
- Status changed from Feedback to Closed
- % Done changed from 90 to 100
added tests
closing