The bug is apparently in $SAGE_ROOT/devel/sage/sage/matrix2.pyx, in _echelon_in_place_classical indeed:
sage: m=matrix(2,[1.5,1.75,-1.5,-1.75]) sage: set_verbose(10) sage: m.rank() verbose 1 (<module>) generic in-place Gauss elimination on 2 x 2 matrix verbose 1 (<module>) done with gauss echelon form (time = 0.0) 2 (m.rank() delegates to _echelon_in_place_classical() in this case) On Aug 17, 2:20 pm, vgermrk <vger...@googlemail.com> wrote: > I discussed the following issue with <logix> @IRC: > > sage: rank(matrix(2,[1.5,1.75,-1.5,-1.75])) > 2 > > gives a wrong answer. > > Multiplying with a full rank matrix also gives unexpected results: > > sage: rank( matrix(2,2,[1,0,0,1]) * matrix(2,[1.5,1.75,-1.5,-1.75]) ) > 2 > sage: rank( matrix(2,2,[1,0,1,1]) * matrix(2,[1.5,1.75,-1.5,-1.75]) ) > 1 > > And even more serious: multiplying with another rank one matrix: > > sage: rank( matrix(2,2,[1,0,1,0]) * matrix(2,[1.5,1.75,-1.5,-1.75]) ) > 2 > > I think this is something that should be fixed. > -vgermrk- -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
