how to declare int1024 in C#? i can use VB or C++ Too.
Regards
Behrooz
See this question: Big integers in C#
From the answer to that question:
MS is going to introduce System.Numerics.BigInteger class in .NET 4.0
Until then, look at 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.
And by that do you mean a 1024-bit integer? Better wait until BigInteger in 4.0. Until then, the cheekiest you can do with the core libraries is to (ab)use decimal, which has 96 bits for the integer part. Or use a 3rd-party dll.
Just for avoidance of doubt:
public int int1024 = 1024;
If I understand you correctly you want a 1024 bit integer.
Unfortunately there is no inbuilt 1024 bit integer type in .net. You would have to find a specialised library for that kind of thing or write one yourself.
There is an article about big integers here.
Related
We've been trying to implement a new number that can be any amount of bytes because we need a lot of precision during calculation. As well as that we're working in Unity Burst which at the moment does not support anything bigger then a float.
We've been doing this by using a byte array and implementing binary addition, subtraction, multiplication and division. And this is partly working.
The problem we're walking into is that the performance is way slower then the integer math.
So it will produce the following:
4*3 run 100.000 with int's will take about 0-1 milliseconds
4*3 run 100.000 with our number will take about 100 milliseconds
So the question is if we could use the same kind of implementation by inheriting or copying the integer math code. Or even just get a look at how it's implemented? I looked in the C# source code but can't quite find the actual math.
Any help or ideas would be appreciated.
As Tim Rutter suggested in the comments, take a look at the BigInteger class in .NET docs.
It isn't supported in the old Mono c# 2.0, but it is supported since .NET 4x in Unity 2017.1
To use it with burst compiler, you can convert the BigInteger instance to a byte array, as shown here.. I guess it would be similar to your workflow, except that you have to convert it back to BigInteger when making calculations.
If that doesn't work, I suggest taking a look at the first answer here, as it provides a solution for a custom BigInteger class (I haven't tried or tested it)
I'm trying to prototype an unsigned BigInteger type with fixed byte size. The general idea is to have a struct with a fixed buffer of UInt64 parts.
In order to do addition of those big integers efficiently, I could use a C# equivalent of the _addcarry_u64 intrinsic function, as supported by MSVC or ICC in the C++ world.
So far, I unfortunately couldn't find a baked-in equivalent in .NET Core 2.1.
Is there any equivalent in the C# world already (maybe with .NET Core 3.0 intrinsics? I can't test that on my machine unfortunately)?
Alternatively, is there any reasonable way for a custom implementation?
The only way I can think of would be to generate Assembly for these instructions, but then again, the only ways I've seen to invoke Assembly at all from C# is via PInvoke, and - to be tested - but I'd strongly suppose the overhead of that will be considerable larger than the performance to be gained from the intrinsic in the first place.
Thanks
Does anybody know of a way I can calculate very large integers in c#
I am trying to calculate the factorial of numbers e.g.
5! = 5*4*3*2*1 = 120
with small numbers this is not a problem but trying to calculate the factorial of the bigest value of a unsigned int which is 4,294,967,295 it doesn't seem possible.
I have looked into the BigInteger class but it doesn't seem to do what I need
any help would be greatly appreciated
To calculate the factorial of uint.MaxValue you'd need a lot of storage.
For example, the Wikipedia article as 8.2639316883... × 10^5,565,708. You're going to gain information like crazy.
I strongly suspect you're not going find any way of calculating it on a sane computer in a sane amount of time. Why do you need this value? Would Stirling's approximation be close enough?
Firstly, it's worth pointing out that the factorial of uint.MaxValue is astronomically large. I'm not able to find a good estimate of the order of magnitude of its factorial, but its bit representation will probably occupy a high percentage of a standard RAM, if not well exceed.
A BigInteger class seems to be what you want, providing you only want to go up to around 1,000,000 or so (very roughly). After that, time and memory become very prohibitive. In current (stable) versions of .NET, up to 3.5, you have to go with a custom implementation. This one on the CodeProject seems to be highly rated. If you happen to be developing for .NET 4.0, the Microsoft team have finally gotten around to including a BigInteger class in the System.Numerics namespace of the BCL. Unlike some BigInteger implementations, the one existing in .NET 4.0 doesn't have a built-in factorial method (I'm not sure about the CodeProject one), but it should be trivial to implement one - an extension method would be a nice way.
Since you seem to think you don't want to use a BigInteger type, it would be helpful if you could verify that it's not what you want having read my reply, and then explain precisely why it doesn't suit your purposes.
4294967295! = 10^(10^10.597) ~ 10^(40000000000)
This value requires about 40 Gb of RAM to store, even if you will find any BigInteger implementation for C#!
P.S. Well, with optimized storing, let's say 9 digits in 4 bytes, it will take ~18 Gb of RAM.
Why do you think that you need to calculate those factorials? It's not practiacally useful for anything to do the actual calculations.
Just the result of calculating factorial of (2^32-1) would take up a lot of space, approximately 16 GB.
The calculation itself will of course take a lot of time. If you build the program so that you can transfer the calculation process to faster hardware as it is invented, you should be able to get the result within your lifetime.
If it's something like an Euler problem that you are trying to solve, consider that a lot of solutions are found by elliminating what it is that you actually don't have to calculate in order to get the answer.
Here .
The fastest one, straight from the Factorial Man - Peter Luschny.
You can use the BigInteger class from the J# libraries for now. Here's an article on how. It makes deployment harder because you have to send out the J# redistributable. You can also consider going to VS2010 beta as Framework 4.0 will have BigInteger.
In case you have J# redist installed, an alternative way would be using java.math.BigInteger by adding a reference to the vjslib assembly.
Try to use an array for this task. You could use as long integers as you have free memory space. Every member of array repsesents one decimal digit. The only you need is to implement multipication.
If you are doing calculations with factorials like combinations for example you rarely need to multiply all the way down to 1 (eg. 98 * 98 * 97 since everything else cancels out).
I need to do some large integer math. Are there any classes or structs out there that represent a 128-bit integer and implement all of the usual operators?
BTW, I realize that decimal can be used to represent a 96-bit int.
It's here in System.Numerics. "The BigInteger type is an immutable type that represents an arbitrarily large integer whose value in theory has no upper or lower bounds."
var i = System.Numerics.BigInteger.Parse("10000000000000000000000000000000");
While BigInteger is the best solution for most applications, if you have performance critical numerical computations, you can use the complete Int128 and UInt128 implementations in my Dirichlet.Numerics library. These types are useful if Int64 and UInt64 are too small but BigInteger is too slow.
System.Int128 and System.UInt128 have been available since .NET Core 7.0 Preview 5
They were implemented in Add support for Int128 and UInt128 data types
I don't know why they aren't in the .NET 7 Preview 5 announcement but in the upcoming .NET 7 Preview 6 announcement there'll also be Int128Converter and UInt128Converter for the new types in Preview 5
They didn't have C# support yet though, just like System.Half, so you'll have to use Int128 explicitly instead of using a native C# keyword
No, there's nothing in .NET <= 3.5. I'm hoping/expecting that BigInteger will make its return in .NET 4.0. (It was cut from .NET 3.5.)
BigInteger is now a standard part of C# and friends in .NET 4.0. See: Gunnar Peipman's ASP.NET blog.
Note that the CPU can generally work with ordinary integers much more quickly and in constant time, especially when using the usual math operators (+, -, /, ...) because these operators typically map directly to single CPU instructions.
With BigInteger, even the most basic math operations are much slower function calls to methods whose runtime varies with the size of the number. This is because BigInteger implements arbitrary precision arithmetic, which adds considerable but necessary overhead.
The benefit is that BigIntegers are not limited to 64 or even 128 bits, but by available system memory (or about 264 bits of precision, whichever comes first).
Read here.
GUID is backed by a 128 bit integer in .NET framework; though it doesn't come with any of the typical integer type methods.
I've written a handler for GUID before to treat it as a 128 bit integer, but this was for a company I worked for ~8 years ago. I no longer have access to the source code.
So if you need native support for a 128 bit integer, and don't want to rely on BigInteger for whatever reason, you could probably hack GUID to server your purposes.
If you don't mind making reference to the J# library (vjslib.dll included with VS by default) there is already and implementation of BigInteger in .NET
using java.math;
public static void Main(){
BigInteger biggy = new BigInteger(....)
}
C# PCL library for computations with big numbers such as Int128 and Int256.
https://github.com/lessneek/BigMath
I believe Mono has a BigInteger implementation that you should be able to track down the source for.
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?
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.
F# also ships with one. You can get it at Microsoft.FSharp.Math.
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).
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.
Here are several implementations of BigInteger in C#.
I've used Mono's BigInteger implementation, works pretty fast (I've used it in CompactFramework)
Bouncy Castle
Mono
I'm not sure about the performance, but IronPython also has a BigInteger class. It is in the Microsoft.Scripting.Math namespace.
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.
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.
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?
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.
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
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.