Precision bug in roots:

[alexjbest]

sage: from sage_cluster_pictures.cluster_pictures import *
....: K = Qp(3)
....: x = polygen(K)#y = polygen(L)
....: H = HyperellipticCurve((x+5)*(x+4)*(x-13)*x*(x-3)*(x-4))
....: R = Cluster.from_curve(H)
....: %display ascii_art
....: R
....:
....:
(* (* *)_1 (* * *)_2)_0
sage: s1 = R.children()[2]
sage: s1.roots()
[ 1 + 3 + 3^2 + 2*3^16 + 2*3^17 + 2*3^18 + 3^19 + O(3^20),

 1 + 3 + 2*3^16 + 2*3^18 + O(3^20),

 1 + 3 + 2*3^2 + 2*3^3 + 2*3^4 + 2*3^5 + 2*3^6 + 2*3^7 + 2*3^8 + 2*3^9 + 2*3^10 + 2*3^11 + 2*3^12 + 2*3^13 + 2*3^14 + 2*3^15 + 3^16 + 2*3^17 + O(3^20) ]

[rbommel]

Is this actually a sage error? It could be that these are roots in the ring Qp(3, 20) = Z/3^20 though, but that would be very confusing.

[alexjbest]

Probably yes, I just wanted to keep track of it so we can workaround?

On Thu, Jun 25, 2020 at 5:04 AM rbommel notifications@github.com wrote:

Is this actually a sage error?

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[rbommel]

So when does this cause a problem? Because I think sage already complains if there is not enough precision to determine whether or not two roots are different.

[alexjbest]

Well in the example I gave it loses 4 / 20 digits, which is a psychological problem for me, if my roots are of ((x+5)(x+4)(x-13)x(x-3)*(x-4)) I want to see -5,-4,13,0,3,4 as my roots.

[rbommel]

Well, then I would suggest to file this with sage, and not here.