#597 is not finished and it might still have some little performance issues. So I think it's easier to simply use Piranha as is. @rwst I think Piranha polynomials support rational exponents, and that's all we need. I think Piranha has some support for power series as well, but we don't need to use it if it doesn't support rational exponents. We can base it on top of our own polynomials. One problem with Piranha is that I think it doesn't compile using MSVC, so it can only be an optional dependency, and so we need to have some kind of polynomials that work on all platforms. But when it comes to benchmarking, I wanted to use Piranha directly, to get us an idea about what the speed can be. Thanks for the Pari benchmark, we should benchmark against it as well.