On Thu, Mar 19, 2009 at 9:33 PM, Rob Beezer wrote:
>
> Chris,
>
> Some flakiness with Google Groups. Here's the rest of what I wanted
> to say.
>
> Sage is *very* fast over ZZ, and I know you said that was irrelevant.
> Use the command in the previous message to scale out the fractions, do
> you
Chris,
Some flakiness with Google Groups. Here's the rest of what I wanted
to say.
Sage is *very* fast over ZZ, and I know you said that was irrelevant.
Use the command in the previous message to scale out the fractions, do
your computation, and then move the scalar back in to the result. Not
Chris,
I'm having trouble posting a reply here. Here's the essence of what I
wanted to show you. Perhaps more in just a minute.
sage: m=matrix(QQ, [[3/2, 4/3], [1/7, 5/11])
sage: m._clear_denoms()
([693 616]
[ 66 210], 462)
Rob
On Mar 19, 8:13 pm, Mike Hansen wrote:
> On Mar 19, 6:54 pm, C
On Mar 19, 6:54 pm, Chris Godsil wrote:
> What algorithm(s) does sage use to compute determinants over QQ[t] or
> QQ[t,u]?
For both of these, it is computing them using minors, which is awful
when the matrices are not tiny.
> Does they work over the ring of definition, or over the field of
> fr
Hi Chris,
I'm not sure what other types of matrices you're looking at, but if
the matrices are similar to the ones you posted, then one typical
approach is to evaluate the matrices at a number of points, take the
determinant, and then rebuild the determinant from that data. This
work well if you
Hi Chris,
On Fri, Mar 20, 2009 at 1:54 AM, Chris Godsil wrote:
>
> As the Reference Manual suggests, I
> entered
> M.determinant? to see what algorithm was being used, but did not get
> any useful information.
For the specified matrix M as defined above in your original email, I
entered this
Thanks for your comments so far. Please note that I want to compute
determinants of
matrices whose entries are polynomials over QQ (so performance over ZZ
is irrelevant).
For the examples I offered, the determinants were characteristic
polynomials
but this would not be true for the cases I want t
Hi Chris,
On Thu, Mar 19, 2009 at 8:17 AM, Chris Godsil wrote:
>
> I want to compute determinants of matrix polynomials, for matrices up
> to 20 x 20, say.
> The attached transcript seems to indicate 9 or 10 might be my limit.
> (Or it's late
> and I am being stupd?)
>
>
On Mar 19, 2009, at 1:17 AM, Chris Godsil wrote:
> I want to compute determinants of matrix polynomials, for matrices up
> to 20 x 20, say.
> The attached transcript seems to indicate 9 or 10 might be my limit.
> (Or it's late and I am being stupd?)
It depends on what ring you're over.
sage: M
