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 | 1 | initial version |
Thanks for reporting this bug here and on Sage Trac:
To analyse the error coming from:
sage: M = Matrix([0], ring=GF(4))
sage: M
[0]
sage: M.inverse()
[1]
we can check the documentation and the source code
for the inverse method of M:
sage: M.inverse?
sage: M.inverse??
and we see that it calls ~M. In Sage, ~M calls
M.__invert__().
The source code for the __invert__ method revealed by
sage: M.__invert__??
involves mzed_invert_newton_john from m4rie.
The source code for that function is at
- https://github.com/malb/m4rie/blob/9f39ae950a733bd1e9ced74f59d9b594f5a7296c/src/newton_john.c#L508
and it echelonizes the augmented matrix to compute the inverse --- a fine thing to do for an invertible matrix.
There is now a fix at the Sage Trac ticket. After the fix, we first check whether the matrix has full rank; if not, we raise an error; if yes, we compute the inverse by echelonizing the augmented matrix.
