Big integers in C#
biginteger, c#, j#, largenumber
Solution
As of .NET 4.0 you can use the System.Numerics.BigInteger class. See documentation here: http://msdn.microsoft.com/en-us/library/system.numerics.biginteger(v=vs.110).aspx
Another alternative is the IntX class.
IntX is an arbitrary precision integers library written in pure C# 2.0 with fast - O(N * log N) - multiplication/division algorithms implementation. It provides all the basic operations on integers like addition, multiplication, comparing, bitwise shifting etc.
Problem
Currently I am borrowing `java.math.BigInteger` from the J# libraries as described here. Having never used a library for working with large integers before, this seems slow, on the order of 10 times slower, even for `ulong` length numbers. Does anyone have any better (preferably free) libraries, or is this level of performance normal?