charpoly very, very slow
- Subject: charpoly very, very slow
- From: Oliver Kullmann
- Date: Fri, 23 May 2008 18:17:40 +0100
Aha, thanks!
Oliver
On Fri, May 23, 2008 at 11:50:27AM -0500, Barton Willis wrote:
> Try setting ratmx to true:
>
> (%i27) m :
> matrix([0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4],[1,0,2,1,2,1,3,2,2,1,3,2,3,2,4,3],
>
> [1,2,0,1,2,3,1,2,2,3,1,2,3,4,2,3],[2,1,1,0,3,2,2,1,3,2,2,1,4,3,3,2],
>
> [1,2,2,3,0,1,1,2,2,3,3,4,1,2,2,3],[2,1,3,2,1,0,2,1,3,2,4,3,2,1,3,2],
>
> [2,3,1,2,1,2,0,1,3,4,2,3,2,3,1,2],[3,2,2,1,2,1,1,0,4,3,3,2,3,2,2,1],
>
> [1,2,2,3,2,3,3,4,0,1,1,2,1,2,2,3],[2,1,3,2,3,2,4,3,1,0,2,1,2,1,3,2],
>
> [2,3,1,2,3,4,2,3,1,2,0,1,2,3,1,2],[3,2,2,1,4,3,3,2,2,1,1,0,3,2,2,1],
>
> [2,3,3,4,1,2,2,3,1,2,2,3,0,1,1,2],[3,2,4,3,2,1,3,2,2,1,3,2,1,0,2,1],
>
> [3,4,2,3,2,3,1,2,2,3,1,2,1,2,0,1],[4,3,3,2,3,2,2,1,3,2,2,1,2,1,1,0])$
> (%i28) ratmx : true$
>
>
> (%i29) charpoly(m,'x);
> Evaluation took 0.0100 seconds (0.0100 elapsed)
> (%o29) x^16-640*x^14-10240*x^13-61440*x^12-131072*x^11
>
> Question: Should charpoly automatically set ratmx to true?
>
> Barton
>
> -----maxima-bounces at math.utexas.edu wrote: -----
>
> >To: maxima at math.utexas.edu
> >From: Oliver Kullmann <O.Kullmann at swansea.ac.uk>
> >Sent by: maxima-bounces at math.utexas.edu
> >Date: 05/23/2008 11:19AM
> >Subject: charpoly very, very slow
> >
> >Hi,
> >
> >(%i6) M;
> >(%o6)
> >matrix([0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4],[1,0,2,1,2,1,3,2,2,1,3,2,3,2,4,3]
> >,
> >
> >[1,2,0,1,2,3,1,2,2,3,1,2,3,4,2,3],[2,1,1,0,3,2,2,1,3,2,2,1,4,3,3,2],
> >
> >[1,2,2,3,0,1,1,2,2,3,3,4,1,2,2,3],[2,1,3,2,1,0,2,1,3,2,4,3,2,1,3,2],
> >
> >[2,3,1,2,1,2,0,1,3,4,2,3,2,3,1,2],[3,2,2,1,2,1,1,0,4,3,3,2,3,2,2,1],
> >
> >[1,2,2,3,2,3,3,4,0,1,1,2,1,2,2,3],[2,1,3,2,3,2,4,3,1,0,2,1,2,1,3,2],
> >
> >[2,3,1,2,3,4,2,3,1,2,0,1,2,3,1,2],[3,2,2,1,4,3,3,2,2,1,1,0,3,2,2,1],
> >
> >[2,3,3,4,1,2,2,3,1,2,2,3,0,1,1,2],[3,2,4,3,2,1,3,2,2,1,3,2,1,0,2,1],
> >
> >[3,4,2,3,2,3,1,2,2,3,1,2,1,2,0,1],[4,3,3,2,3,2,2,1,3,2,2,1,2,1,1,0])
> >(%i7) charpoly(M,x);
> >
> >This runs now already for a day!
> >
> >Computing the characteristic polynomial is somewhat more expensive than
> >Gaussian
> >elimination, but not too much, and so I believe something is wrong here.
> >
> >Oliver
> >_______________________________________________
> >Maxima mailing list
> >Maxima at math.utexas.edu
> >http://www.math.utexas.edu/mailman/listinfo/maxima
--
Dr. Oliver Kullmann
Computer Science Department
Swansea University
Faraday Building, Singleton Park
Swansea SA2 8PP, UK
http://cs.swan.ac.uk/~csoliver/