Ewan Delanoy on Thu, 22 Jan 2026 14:57:11 +0100


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Computation with two algebraic integers


I have two algebraic integers g and h, and

- I know the minimal polynomial of g, stored in a variable called minpoly_for_g, which has degree 18 in g
- I know the minimal polynomial of h, stored in a variable called minpoly_for_h, which has degree 72 in h
- I also know an extra relation between g and h, in the form of a polynomial with integer coefficients called
relator, and which has degree 17 in g, 71 in h. This relation ensures that g is unique in terms of h.

My goal is to compute the (polynomial) _expression_ of g in terms of h from those data. So far, all my attempts failed
because of integer overflow at some point. For example, the most obvious method of applying the Euclidean algorithm
overflows after a few iterations.

Any suggestions to attack this problem ?

To give an idea in terms of size, sizebyte(minpoly_for_h)=11432, sizebyte(minpoly_for_g)=824, sizebyte(relator)=6184.