Le samedi 24 mai 2014 16:29:38 UTC+2, Tom Harris a écrit :
> Now I have some code to generate the polynomial which I am interested in,
> I store it as p:
>
> p = (output of some functions)
>
> ( p is ((x1^3 - 2*x1*x2 + x3)*c1^2 - (x1*x2 - x3)*c1 + x3)*c2^2 + x1^3 +
> c1^2*x3 - (x1*x2 - x3)*c1 - ((x1*x2 - x3)*c1^2 - (x1^3 - x1*x2 + x3)*c1 +
> x1*x2 - x3)*c2 - 2*x1*x2 + x3)
>
> Now the curious thing: p is (naively at least) symmetric in c1 and c2, but
> calling ElemSym(p) returns an error:
>
> ValueError: x0 + 2*x1 + x2 is not a symmetric polynomial
>
> but if I copy the polynomial itself and call
>
> ElemSym(((x1^3 - 2*x1*x2 + x3)*c1^2 - (x1*x2 - x3)*c1 + x3)*c2^2 + x1^3 +
> c1^2*x3 - (x1*x2 - x3)*c1 - ((x1*x2 - x3)*c1^2 - (x1^3 - x1*x2 + x3)*c1 +
> x1*x2 - x3)*c2 - 2*x1*x2 + x3)),
>
> then it works and I get
>
> (x1^3-2*x1*x2+x3)*e[] + (-x1*x2+x3)*e[1] + x3*e[1, 1] +
> (x1^3-x1*x2-x3)*e[2] + (-x1*x2+x3)*e[2, 1] + (x1^3-2*x1*x2+x3)*e[2, 2] +
> (3*x1*x2-3*x3)*e[3] + (-2*x1^3+4*x1*x2-2*x3)*e[3, 1] +
> (2*x1^3-4*x1*x2+2*x3)*e[4]
>
> as expected.
>
> Can somebody help me understand what is going on here?
>
Maybe the output of your function does not live in C?
Instead of ElemSym(p), you could try:
ElemSym(C(p))
or
p = C(p)
ElemSym(p)
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