Done
http://sagetrac.org/sage_trac/ticket/1219
On Nov 20, 2007 2:22 PM, William Stein <[EMAIL PROTECTED]> wrote:
>
>
> On Nov 20, 2007 11:14 AM, David Joyner <[EMAIL PROTECTED]> wrote:
> >
> > Hi:
> >
> > Something funny is going on:
> >
> > sage: MS = MatrixSpace(CC, 2, 2)
> > sage: A = MS([[1,5],[3,-1]])
> > sage: A.eigenspaces()
> >
> > [
> > (4.00000000000000, [
> > (1.00000000000000, 1.00000000000000)
> > ]),
> > (-4.00000000000000, [
> >
> > ])
> > ]
> > sage: A.eigenspaces()[0]
> >
> > (4.00000000000000, [
> > (1.00000000000000, 1.00000000000000)
> > ])
> > sage: A.eigenspaces()[1]
> >
> > (-4.00000000000000, [
> >
> > ])
> > sage: MS = MatrixSpace(QQ, 2, 2)
> > sage: A = MS([[1,5],[3,-1]])
> > sage: A.eigenspaces()
> >
> > [
> > (4, [
> > (1, 1)
> > ]),
> > (-4, [
> > (1, -5/3)
> > ])
> > ]
> >
> > I find it strange that eigenspaces works for QQ
> > but not for the larger field CC. Makes me think
> > the problem isn't with eigenspaces at all ...
> > Should I create a trac item under linear algebra
> > or ???
>
> Yes make a trac ticket. The issue above is undoubtedly that
> there is no specialized implementation of matrices over CC.
> It's just completely generic code. So some generic echelon
> is going wrong. If you want something that actually works
> very efficiently now, use CDF, which has the advantage that
> it will scale to HUGE problems:
>
>
> {{{id=0|
> m = matrix(CDF,[[1,5],[3,-1]])
> }}}
>
> {{{id=1|
> m.eigenspaces()
> ///
> ([4.0, -4.0], [Vector space of degree 2 and dimension 1 over Complex
> Double Field
> User basis matrix:
> [ 0.707106781187 -0.514495755428], Vector space of degree 2 and
> dimension 1 over Complex Double Field
> User basis matrix:
> [0.707106781187 0.857492925713]])
> }}}
>
> >
>
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