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?
asked Oct 7, 2008 at 0:16
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nice link. A couple of gems there.– Mitch WheatCommented Oct 7, 2008 at 0:34
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3Only problem is that they require the J# redistributables to be installed. The fact that J# is all but dead (it wasn't in VS 2008 atleast) probably doesn't help with promoting that.– Matthew ScharleyCommented Oct 7, 2008 at 0:39
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J# is just to facilitate the migration of existing Java projects to .NET. I definitely wouldn't incorporate any of its libraries into a new project.– MusiGenesisCommented Oct 7, 2008 at 1:44
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possible duplicate of [How can I represent a very large integer in .NET? ](stackoverflow.com/questions/25375/…)– Roger PateCommented May 26, 2010 at 22:27
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@Roger: I'd rather close the other, as this one has more up to information attached to it.– Matthew ScharleyCommented May 27, 2010 at 8:14
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13 Answers
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.
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27For the record, The
System.Numericsassembly is not referenced by default in new projects, so this needs to be added beforeBigIntegercan be used. Commented Dec 5, 2010 at 16:45 -
In Solution Explorer do right click on References > Add Reference > Search for numerics and check the found reference. Now you can add "using System.Numerics;" at the top of your .cs file– JanCommented Oct 14, 2016 at 12:59
F# also ships with one. You can get it at Microsoft.FSharp.Math.
answered Jan 31, 2009 at 13:22
The System.Numerics.BigInteger class in .NET 4.0 is based on Microsoft.SolverFoundation.Common.BigInteger from Microsoft Research.
The Solver Foundation's BigInteger class looks very performant. I am not sure about which license it is released under, but you can get it here (download and install Solver Foundation and find the Microsoft.Solver.Foundation.dll).
answered Jun 19, 2009 at 17:48
I reckon you could optimize the implementation if you perform all the operations on BigInts that are going to return results smaller than a native type (Eg. int64) on the native types and only deal with the big array if you are going to overflow.
edit This implementation on codeproject, seems only 7 times slower ... But with the above optimization you could get it to perform almost identically to native types for small numbers.
answered Oct 7, 2008 at 0:33
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I believe the J# library uses Byte's internally, it has a ToByteArray() function atleast, and no other ToArray() function. This might be an idea if I wanted to roll my own, I'm not too thrilled with that idea either though. Commented Oct 7, 2008 at 0:37
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What size data are you working with, in general? Will stuff overflow the Int64 size on a regular basis, or is it an exception? Commented Oct 7, 2008 at 0:44
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I'm doing it mostly on a case by case basis, setting it to BigInt when I run into an overflow with a checked{} block. If it does that once, then there's a pretty good chance it'll do it repeatedly and often. Commented Oct 7, 2008 at 0:58
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1monoxide, I don't think it will be easy to get this to perform much faster than the implementation on codeproject for large numbers. Commented Oct 7, 2008 at 1:35
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Like I said in my original post, I've never used a BigInteger implementation before, so I wouldn't know what sort of performance they get. That was more the question I was asking. Damn, I still want to roll my own as an intellectual excercise now though :( Commented Oct 7, 2008 at 2:13
Here are several implementations of BigInteger in C#. I've used Mono's BigInteger implementation, works pretty fast (I've used it in CompactFramework)
I'm not sure about the performance, but IronPython also has a BigInteger class. It is in the Microsoft.Scripting.Math namespace.
answered Oct 7, 2008 at 0:20
Yes, it will be slow, and 10x difference is about what I'd expect. BigInt uses an array to represent an arbitrary length, and all the operations have to be done manually (as opposed to most math which can be done directly with the CPU)
I don't even know if hand-coding it in assembly will give you much of a performance gain over 10x, that's pretty damn close. I'd look for other ways to optimize it--sometimes depending on your math problem there are little tricks you can do to make it quicker.
I used Biginteger at a previous job. I don't know what kind of performance needs you have. I did not use it in a performance-intensive situation, but never had any problems with it.
answered Oct 7, 2008 at 0:29
This may sound like a strange suggestion, but have you tested the decimal type to see how fast it works?
The decimal range is ±1.0 × 10^−28 to ±7.9 × 10^28, so it may still not be large enough, but it is larger than a ulong.
There was supposed to be a BigInteger class in .NET 3.5, but it got cut.
answered Oct 7, 2008 at 0:31
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Yes, I saw that anouncement when originally looking for a BigInt library. Makes me sad. Oh well. Commented Oct 7, 2008 at 0:34
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You would have to be careful - using a decimal might cause rounding issues. Commented Oct 7, 2008 at 0:40
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Decimal doesn't cause rounding errors. It's not floating point.– KibbeeCommented Oct 7, 2008 at 0:57
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2Decimal only tries to minimize errors due to rounding. It is not immune to rounding. msdn.microsoft.com/en-us/library/system.decimal.aspx Commented Oct 7, 2008 at 1:48
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9Decimal is a floating point type. It's just that it's a floating decimal point instead of a floating binary point. See pobox.com/~skeet/csharp/decimal.html I wouldn't expect rounding issues if all values are integers within the appropriate range though. Commented Oct 7, 2008 at 6:10
This won't help you, but there was supposed to be a BigInteger class in .Net 3.5; it got cut, but from statements made at PDC, it will be in .Net 4.0. They apparently have spent a lot of time optimizing it, so the performance should be much better than what you're getting now.
Further, this question is essentially a duplicate of How can I represent a very large integer in .NET?
answered Nov 8, 2008 at 20:41
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BigInteger is in 3.5 but its an internal class. ;) Its there just not ready for prime time. Commented Jan 31, 2009 at 13:25
See the answers in this thread. You will need to use one of the third-party big integer libraries/classes available or wait for C# 4.0 which will include a native BigInteger datatype.
answered Nov 10, 2008 at 20:28
This Looks very promising. It is a C# Wrapper over GMP.
http://web.rememberingemil.org/Projects/GnuMpDotNet/GnuMpDotNet.html
There are also other BigInteger options for .Net here in particular, Mpir.Net
answered Aug 25, 2015 at 1:39
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1Mpir.NET is partly based on Emil's GMP wrapper. The other part is X-MPIR, and fused together you get the convenience of Emil's wrapper and the performance of X-MPIR. Commented Dec 10, 2015 at 12:53
You can also use the Math.Gmp.Native Nuget package that I wrote. Its source code is available on GitHub, and documentation is available here. It exposes to .NET all of the functionality of the GMP library which is known as a highly-optimized arbitrary-precision arithmetic library.
Arbitrary-precision integer are represented by the mpz_t type. Operations on these integers all begin with the mpz_ prefix. For examples, mpz_add or mpz_cmp. Source code examples are given for each operation.
answered May 18, 2019 at 9:10
