Opened 8 years ago
Last modified 8 years ago
#12020 closed defect
bug in zero_matrix rewrite in matrix_space.py — at Version 4
Reported by: | was | Owned by: | jason, was |
---|---|---|---|
Priority: | blocker | Milestone: | sage-4.8 |
Component: | linear algebra | Keywords: | |
Cc: | vbraun | Merged in: | |
Authors: | William Stein | Reviewers: | |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
Observe this:
sage: D=DirichletGroup(20); sage: g=D[7].extend(400); #order 4 character sage: M=ModularSymbols(g,2,sign=1).cuspidal_subspace() sage: N=M.new_subspace() TypeError Traceback (most recent call last) /mnt/usb1/scratch/wstein/ref/sage-4.8.alpha2-sage.math.washington.edu-x86_64-Linux/local/lib/python2.6/site-packages/sage/rings/number_field/number_field.pyc in _coerce_non_number_field_element_in(self, x) 5399 except (TypeError, AttributeError), msg: 5400 pass -> 5401 raise TypeError, type(x) 5402 5403 def _coerce_from_str(self, x): TypeError: <type 'NoneType'>
Debugging we see that the problem is that this code in matrix_space.py:
479 if entries is None or entries == 0: 480 if self._copy_zero: # faster to copy than to create a new one. 481 return self.zero_matrix().__copy__() 482 else: --> 483 return self.__matrix_class(self, None, coerce=coerce, copy=copy)
That None in the last line is then coerced for some reason into a number field (Cyclotomic Field of order 4 and degree) which makes no sense now...
This bug was introduced in #11589.
Apply trac_12020.2.patch
Change History (6)
comment:1 Changed 8 years ago by
comment:2 Changed 8 years ago by
Here is a simple test to reveal the bug. Small size matrices don't show the bug, probably because of some arbitrary caching parameter in #11589, which is probably why this bug slipped through our test framework (we *really* need a random larger testing framework!):
sage: A = MatrixSpace(CyclotomicField(4),60,30)(0) sage: A.augment(A) boom!
comment:3 Changed 8 years ago by
- Summary changed from major (BLOCKER!) bug probably in matrix_space.py to bug in zero_matrix rewrite in matrix_space.py
Changed 8 years ago by
comment:4 Changed 8 years ago by
- Description modified (diff)
- Status changed from new to needs_review
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I figured this out. This bug was introduced by #11589 (by Simon King and Martin Albrecht). Basically the zero_matrix() method's code was "mangled/changed" (?) when being copied into the init method by replacing "0" by "None". This breaks the code, since there is no reason that None be coercible into a ring R, and I don't think that has to be supported because, e.g., in Python
int(None)
is an error. Also, this is a weird change since the zero_matrix method in the new code still uses 0.Patch coming up.