Singular provides a massive and mature library for Gröbner bases,
multivariate polynomial gcds, bases of Riemann-Roch spaces of a plane
curve, and factorizations, among other things. We illustrate
multivariate polynomial factorization using the Sage interface to
Singular (do not type the ...
):
sage: R1 = singular.ring(0, '(x,y)', 'dp') sage: R1 // characteristic : 0 // number of vars : 2 // block 1 : ordering dp // : names x y // block 2 : ordering C sage: f = singular('9*y^8 - 9*x^2*y^7 - 18*x^3*y^6 - 18*x^5*y^6 + \ ... 9*x^6*y^4 + 18*x^7*y^5 + 36*x^8*y^4 + 9*x^10*y^4 - 18*x^11*y^2 - \ ... 9*x^12*y^3 - 18*x^13*y^2 + 9*x^16')
Now that we have defined
, we print it and factor.
sage: f 9*x^16-18*x^13*y^2-9*x^12*y^3+9*x^10*y^4-18*x^11*y^2+36*x^8*y^4 +18*x^7*y^5-18*x^5*y^6+9*x^6*y^4-18*x^3*y^6-9*x^2*y^7+9*y^8 sage: f.parent() Singular sage: F = f.factorize(); F [1]: _[1]=9 _[2]=x^6-2*x^3*y^2-x^2*y^3+y^4 _[3]=-x^5+y^2 [2]: 1,1,2 sage: F[1][2] x^6-2*x^3*y^2-x^2*y^3+y^4
As with the GAP example in Section 4.2, we can compute
the above factorization without explicitly using the Singular interface
(however, behind the scenes Sage uses the Singular interface
for the actual computation). Do not type the ...
:
sage: x, y = QQ['x, y'].gens() sage: f = 9*y^8 - 9*x^2*y^7 - 18*x^3*y^6 - 18*x^5*y^6 + 9*x^6*y^4\ ... + 18*x^7*y^5 + 36*x^8*y^4 + 9*x^10*y^4 - 18*x^11*y^2 - 9*x^12*y^3\ ... - 18*x^13*y^2 + 9*x^16 sage: factor(f) (9) * (-x^5 + y^2)^2 * (x^6 - 2*x^3*y^2 - x^2*y^3 + y^4)
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