BigInteger Is Back

One of the new features in .NET 4.0 is the BigInteger class. This was suppose to be part of 3.5 framework, but after the CTP it was gone. Now it’s back. This big integer is a really large integer representation. However, I was not able to find the precision documented anywhere.

The class is available in the System.Numerics namespace and provides overloaded operators, parsing methods and other utility features for bit integer numbers.

Not very long ago, on codexpert.ro we launched a contest for finding the biggest pair of amicable numbers. One of the members (crystyce) that submited a solution found this big pair (2724918040393706557785752240819405848576, 2724918040396184856306258038787235905536) with a C++ implementation using a 3rd party BigInt class. I decided to put that in C# 4.0 and use BigInteger. Maybe you can find things to optimize in the below code, but that’s not the point here. I’m showing you this code just to get a feeling of BitInteger.

As you can see, it was very fast finding the same big pair. Well it was at least on my 2 core machine.

The only thing I don’t understand about the implementation is the presence of some helper functions in the BigInteger class.

That belongs to System.Math, or maybe to a System.Numerics.Math class. They are all helper functions, not specific to the implementation of the big integer; and the implementation does not depend on the existing of these functions. So they are clearly utility functions. They should go somewhere else. I have submitted this as feedback to Microsoft Connect. If you agree with it, vote for it here. Of course, if you have arguments for the current implementation, you can vote against it too.

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