Singular and Sagemath

[artal@…]

I think this bug is more a sage bug than a singular bug but since its solution may depend on how singular works I put it here. In sage (version 8.1, but 8.0 has the same issue) I have the following code:

R.<x,y>=PolynomialRing?(QQ,order='neglex') f=(y^2+x3)*(y^2+x3+x^{2*y) singular.lib("all.lib") f._singular_().bernstein()}

I guess this is equivalent to the following singular code

LIB "all.lib"; ring r=0,(x,y),ds; poly f=(y2+x3)*(y2+x3+x2y) bernstein(f)

The results differ: -11/7 is a root in the first case, while -4/7 in the second (and I think there are theoretical results that ensure the second one is correct); moreover in both cases, when using bfct -4/7 is the root.

In other cases I had communication problems between singular and sage but I cannot understand what produces (a non evident) mathematical wrong result.

Anyway, thanks for the great work in Singular.

[hannes]

order='neglex' is in Singular called ls. Many commands require for local orderings a degree ordering, i.e. use order='negdegrevlex' in Sage. We will try to add additional checks for valid orderings.