Hi!
I am afraid I don't know a definitive answer to your question.
But at least I find the following a bit strange:
sage: d = M.det()
sage: d == -1
True
sage: d == 0
False
So, the inversion of M should work, I think. Let us do compute
the inverse "manually" (i.e., by applying Gaussian e
I found this over CC and RR as well: the generic matrix inversion in sage
(which is probably what is getting invoked) looks like it's based on
straight-up row reduction: No pivoting (which it wouldn't know how to do in
the generic case). For CC and RR there's PLU decomposition in mpmath which
d
On Tuesday, January 30, 2018 at 3:50:45 PM UTC, Simon Brandhorst wrote:
>
> The following may be a bug or me not understanding p-adic floating point
> computations:
>
>
> sage: R = Qp(2,type='floating-point',print_mode='terse')
> sage: M = Matrix(R,4,[0, 0, 1, 1, 2^20, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1
On Tuesday, January 30, 2018 at 3:50:45 PM UTC, Simon Brandhorst wrote:
>
> sage: M = Matrix(R,4,[0, 0, 1, 1, 2^19, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1])
> sage: M.inverse()
> [ 1048575201]
> [274878955520 5242881 1048575]
> [ 524289
Hi Simon,
Linear Algebra is known to have issues over the p-adics in Sage. The
generic algorithms used are mostly unaware of precision issues. Xavier
Caruso has been working on improving Sage's Linear Algebra capabilities for
example at https://trac.sagemath.org/ticket/23505 and
https://trac.s
Would it make sense to implement a "generic pivot" method, which takes as
an argument a function that does the pivot selection (that would then be
handled separately over RR/CC vs p-adics)?
Kiran
On Wednesday, January 31, 2018 at 2:16:42 AM UTC-8, Nils Bruin wrote:
>
> I found this over CC and
Here is one way (I am not saying it is always a good strategy):
sage: R = Qp(2,type='floating-point',print_mode='terse')
sage: M = Matrix(R,4,[0, 0, 1, 1, 2^20, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1])
sage: Mi = (M.change_ring(QQ)^(-1)).change_ring(R)
sage: Mi
[1048575 0 0 1]
[ 0
Thank you for your replies.
For the application I had in mind it seems that 'floating-point' numbers
are not suitable.
I was doing computations in
sage: R = Zp(2,type='fixed-mod')
sage: M = Matrix(R,4,[0, 0, 1, 1, 2^19, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1])
sage: M.inverse().base_ring()
2-adic Fiel
