meakk / mpoly

mpoly - a simple header-only C++ polynomial root finder

Usage

There's a single polynomial class available with two functions: evaluate and find_roots

Here's an example:

// define the cubic polynomial: x^3 - 3x^2 + x + 2
auto cubic = mpoly::polynomial<double, 3>({ 1., -3., 1., 2. });

// find all roots between -10 and 10
// returns a vector containing all the roots in the interval
auto roots = cubic.find_roots(-10., 10.);

// That's it! You can double check the roots using evaluate if needed
for (double x : roots)
{
    double y = cubic.evaluate(x);
    // y should be close to zero
}

How to use the library in your project

Clean and modern CMake way

Add this piece of code in your CMake file:

find_package(mpoly REQUIRED)

target_link_library(your_target PRIVATE mpoly::mpoly)

You should be able to include mpoly.h in your code

Quick and dirty way

Just copy mpoly.h in your source tree

How fast and stable is it?

It hasn't been tested extensively but it should be fairly stable and fast if you are looking for roots inside a known interval.
If you tested it and found a bug, feel free to open an issue or a pull request, I'm happy to take a look.

Sources

• "A Fast & Robust Solution for Cubic & Higher-Order Polynomials" by Cem Yuksel
• Numerically stable quadratic solutions