Change Precision of complex_roots()

cshiring
11 ●2

tmonteil
27473 ●32 ●205 ●519 http://wiki.sagemath.o...

I am trying to find the complex roots of the polynomial

poly = x^7 - 6*x^6 + 15*x^5 - 20*x^4 + 15*x^3 - 6*x^2 + x

But when I do poly.complex_roots(), the system gives:

 PariError: overflow in expo()

Apparently there are options for how much precision you want when computing roots -- one option is to use Pari, which is the high-precision option, and the other NumPy, which is the low-precision option. The default is set to use Pari, which apparently overloads when I try to compute the roots of this polynomial (and many others as well, this polynomial is just one example).

How do I change the complex_roots() function to get lower-precision roots?

Comments

How did you define x ? By default, you will get:

sage: poly = x^7 - 6*x^6 + 15*x^5 - 20*x^4 + 15*x^3 - 6*x^2 + x
AttributeError: 'sage.symbolic.expression.Expression' object has no attribute 'complex_roots'

tmonteil ( 7 years ago )

add a comment

sage: poly.roots(ring=CDF) [(0.0, 1), (0.9970597732189228 - 0.0016886658100989547*I, 1), (0.9970597732189228 + 0.0016886658100989547*I, 1), (0.9999846391506835 - 0.003403956023304669*I, 1), (0.9999846391506835 + 0.003403956023304669*I, 1), (1.0029555876303982 - 0.0017152722520868947*I, 1), (1.0029555876303982 + 0.0017152722520868947*I, 1)] sage: poly.roots(ring=QQbar) [(0, 1), (1, 6)] sage: poly.roots(ring=ZZ) [(0, 1), (1, 6)]

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