#8198: p-adic precision in vector multiplication
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Reporter: wuthrich | Owner: roed
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.3
Component: padics | Keywords: padics vector
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Trying to resolve #4656, I found the following unpleasant bug.
this looks good :
{{{
sage: R = Qp(5,5)
sage: x = R(5).add_bigoh(1)
sage: x
O(5)
sage: x*R(1)
O(5)
}}}
But when multiplied with the identity matrix the precision is lost
{{{
sage: I = matrix(R, [[1,0],[0,1]])
sage: v = vector([R(1),x])
sage: v
(1 + O(5^5), O(5))
sage: v*I
(1 + O(5^5), 0)
sage: v[0]*I[1,0] + v[1]*I[1,1]
O(5)
}}}
This causes things like
{{{
sage: M = matrix(R,[[1,2],[3,4]])
sage: M*v
(1 + O(5^5), 3 + O(5^5))
sage: v[0]*M[0,0] + v[1]*M[0,1]
1 + O(5)
sage: v[0]*M[1,0] + v[1]*M[1,1]
3 + O(5)
}}}
This is an even worse example, which could be a different bug
{{{
sage: vv = vector(x)
sage: vv
(0)
sage: vv[0]
0
sage: x
O(5)
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8198>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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