#6442: Random(?) index error with determinant method
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Reporter: spancratz | Owner: somebody
Type: defect | Status: new
Priority: major | Milestone:
Component: algebra | Keywords: det, determinant, IndexError
Reviewer: | Author: Sebastian Pancratz
Merged: |
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On some occasions, the call A.det() for a matrix A results in an error,
namely:
IndexError: list index out of range
The error occurs during the dictionary lookup. It seems that rather than
finding no item (and hence creating a new one and then computing
determinant), an empty item D is found and indexing into D results in the
error.
If run into this strange problem twice during the SAGE Days 16. I've
attached an example file to this email, which contains a saved matrix.
The code
sage: A = load("DetBugMatrix.sobj")
sage: A.det()
should trigger the problem. If I recall correctly, I obtained the matrix
from the following code
sage: R = Zp(p=5,prec=3,type="capped-abs",print_mode="series")
sage: A = random_matrix(R, 10, 10)
Strangely enough (although perhaps not that strange after checking that
the error happens during the lookup), the call A.copy().det() returns the
determinant without any problems.
I have no clue as to how one could systematically reproduce the bug.
In case it may help, I downloaded SAGE 4.0.2 and built it locally. The
machine used is a Lenovo T500 laptop with two intel centrino, running
Ubuntu. If there's any further information that would help, please let me
know.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6442>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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