I think problem is actually due to the inverse using a non-numerically
stable echelon form algorithm for inexact fields. For example, if you
using matrices over RDF:
M=matrix(RDF,[[7,3,10,13],[1,1,2,2],[1,2,3,4],[1,3,5,7]]);det(M);invM=M^(-1);invM*M;det(invM)
you don't get this problem. My gues
On Mon, Jul 1, 2013 at 5:27 AM, David Ingerman wrote:
> On Monday, July 1, 2013 2:06:54 AM UTC-7, Harald Schilly wrote:
>> On Monday, July 1, 2013 10:45:36 AM UTC+2, David Ingerman wrote: The
>> following matrix operation produces wrong answer in online Sage:
>> M=matrix(RR,[[7,3,10,13],[1,1,2,2]
On Monday, July 1, 2013 2:06:54 AM UTC-7, Harald Schilly wrote:
> On Monday, July 1, 2013 10:45:36 AM UTC+2, David Ingerman wrote: The
> following matrix operation produces wrong answer in online Sage:
> M=matrix(RR,[[7,3,10,13],[1,1,2,2],[1,2,3,4],[1,3,5,7]]);det(M);invM=M^(-1);invM*M;det(invM)
>
On Monday, July 1, 2013 10:45:36 AM UTC+2, David Ingerman wrote:
>
> The following matrix operation produces wrong answer in online Sage:
>
> M=matrix(RR,[[7,3,10,13],[1,1,2,2],[1,2,3,4],[1,3,5,7]]);det(M);invM=M^(-1);invM*M;det(invM)
RR stands for the "real numbers" with the usual 53bits of pr
On Monday, July 1, 2013 1:45:36 AM UTC-7, David Ingerman wrote:
> The following matrix operation produces wrong answer in online Sage:
> M=matrix(RR,[[7,3,10,13],[1,1,2,2],[1,2,3,4],[1,3,5,7]]);det(M);invM=M^(-1);invM*M;det(invM)
> If one changes RR to QQ the answers turn correct. Or it is enough
