#5974: [with patch; needs review] the generic linear_combination_of_rows and
linear_combination_of_columns functions for matrices are very stupidly
slotch
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Reporter: was | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-4.0
Component: linear algebra | Keywords:
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Comment(by was):
While making sure all doctests pass for this, I uncovered the following
serious bug:
{{{
sage: e = random_matrix(QQ,1,2,sparse=True);
e.echelon_form().parent().is_dense()
True
sage: type(e)
<type 'sage.matrix.matrix_rational_sparse.Matrix_rational_sparse'>
sage: e = random_matrix(QQ,1,2,sparse=True);
e.echelon_form().parent().is_dense()
True
sage: e = random_matrix(QQ,1,2,sparse=True);
e.echelon_form().parent().is_dense()
True
sage: e = random_matrix(QQ,1,2,sparse=True);
e.echelon_form().parent().is_dense()
True
sage: e = random_matrix(QQ,2,2,sparse=True);
e.echelon_form().parent().is_dense()
False
sage: e = random_matrix(QQ,2,2,sparse=True);
e.echelon_form().parent().is_dense()
True
}}}
We're getting a sparse matrix with *DENSE* parent out of echelon form for
some reason. This totally breaks my new much better implementation of
linear_combination_of_rows, and would of course break all kinds of other
code in random and surprising ways eventually.
The above is all present in the default sage-3.4.2.rc0.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5974#comment:1>
Sage <http://sagemath.org/>
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