C / C++ program suite to factorise 64 bit numbers as quickly as possible.

The program suite incorporates a number of techniques to produce speedy factorisation of numbers, including:

• Using libdivide to speed up the trial division part of the factorisation. Libdivide structures for small primes are pre-calculated in the initialisation, and used to test divisibility using "division by multiplication". See https://libdivide.com/ for details.

• Implementing modular multiplication speedily for moduli below 2^63 using the Rutten-Eekelen technique
  https://www.researchgate.net/publication/220493198_Efficient_and_Formally_Proven_Reduction_of_Large_Integers_by_Small_Moduli Rutten-Eekelen modular multiplication is used in the Miller Rabin tests.

• Using the Fast Primality Testing technique, Michal Forisek, J. Jancina http://ceur-ws.org/Vol-1326/020-Forisek.pdf to perform Miller-Rabin primality testing using only 2 witnesses. Their 64 bit implementation uses Montgomery Multiplication, but my implementation only uses this for larger numbers above 2^43, and uses Rutten-Eekelen for smaller numbers, as it is faster

• Using Montgomery Multiplication in the Pollard Rho part of the factorisatsion, as described in https://projecteuler.chat/viewtopic.php?t=3776 I have modified the code to make use of Visual Studio intrinsics for better performance.

There are a number of experimental and performance testing projects in the solution that can be ignored. The main projects are:

• FactorsDLL, a dynamic link library that can be called from Python. Example Python 3 programs are provided to illustrate how the DLL is called from Python.

• FactorsLib, a static library of the components used in factorisation

• FactorsTest, a set of tests to check the correctness and performance of the factorisation algorithm

• FactorsInteractive, an interactive executable that factorises numbers entered by the user.