C# high precision calculations

Question

Consider this code:

double result = Math.Sqrt(4746073226998689451);

For result I get 2178548422 instead of 2178548421.999999854etc... How can I get more precise result?

Oded · Answer 1 · 2011-11-13T19:10:32.177

7

There is a bunch of high precision maths libraries for .NET mentioned on wikipedia - Arbitrary-percision artithmatic page.

I have seen BigNum recommended here before, though the wikipedia link is broken and I can't find the library elsewhere at the moment.

The other option on the page is the C# binding for MPIR.

edited Nov 13 '11 at 19:10

answered Nov 13 '11 at 18:27

Oded

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@GeorgeDuckett - So it is. Do you have a link to a working site? – Oded Nov 13 '11 at 18:33

score 6 · Accepted Answer · answered Nov 13 '11 at 18:35

For the particular problem, computing the square root, you can use Decimal type and Newton's algorithm:

using System;

class Program
{
  public static void Main()
  {
    long x = 4746073226998689451;
    decimal sqrt_x = (decimal)Math.Sqrt(x);
    for (int i = 0; i < 10; ++i)
      sqrt_x = 0.5m * (sqrt_x + x / sqrt_x);
    Console.WriteLine("{0:F16}", sqrt_x);
  }
}

The result is:

2178548421.9999998547197773

score 1 · Answer 3 · answered Nov 13 '11 at 18:27

1

Using digit by digit calculation will give you as many digits as you are looking for.

answered Nov 13 '11 at 18:27

Emond

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That would be reinventing the wheel. – Dykam Nov 13 '11 at 18:33
@Dykam - Why? I am not suggesting he should code the algorithm himself. If there is an implementation, by all means, use it. – Emond Nov 13 '11 at 18:42
That's true, but there are many algorithms for arbitrary calculations, this is just one. I think it would've been more useful to link to an implementation. – Dykam Nov 13 '11 at 18:47

score 1 · Answer 4 · edited May 23 '17 at 12:26

1

instead of double , try big integer and also check out this link

Big numbers with fraction support

edited May 23 '17 at 12:26

Community

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answered Nov 13 '11 at 18:33

pyCthon

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C# high precision calculations

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