Member Avatar for henryxxll

Hey:
After messing around with Python for some time for large numerical calculations, I realized that Python is just too slow. It's great for smaller numbers, not to mention easy. However, once I start getting into numbers above around five hundred digits in size, it slows down drastically. So, I've looked into C++ for calculations. However, the Integer data type only goes up to around 2 billion (not digits - total value) - not nearly enough.

To combat this problem, I've looked into Bignum libraries, like the GNU MP (GMP) library. However, I just can't seem to understand the documentation that's supplied with GNU MP, as it's mostly geared towards C users, rather than C++ users.

Can someone point me to a nice, well-written tutorial/guide for using GNU MP? I've already googled for one, but the standard manual seems to be about it. If you can't recommend a good set of instructions for GNU MP, can you recommend a better (or, at least, different) bignum/arbitrary-precision library?

Thanks in advance!

Edit:
If there isn't really anything good for C++, is there another language that would be better for large computations?

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Member Avatar for henryxxll

Did you try the online manual available on it's site?

Yes, but it's rather difficult to understand, and not directed towards C++ users...as I already said.

However, I just can't seem to understand the documentation that's supplied with GNU MP, as it's mostly geared towards C users, rather than C++ users.

Member Avatar for henryxxll

All right, I think I've got it. However, I can't figure out how to increase the capacity of the mpz class data type.

Here's my code:

#include <iostream>
#include <gmp.h>
#include <gmpxx.h>



int main()
{
	mpz_class a;
	
	a=1990090990;

	
	std::cout << a << "\n";
	return 0;
}

It returns:

error: ambiguous overload for ‘operator=’ in ‘a = 899996901533920162ll’

How do I increase the capacity?

Member Avatar for mvmalderen

Sure that you don't have to put quotes around the number?

Member Avatar for Peter_APIIT

I don't know GNU Mp is big integer class library. I thought it was just a library with many arithmetic algorithm only.

Please clarify.

Thanks.

Member Avatar for henryxxll

Actually, tux4life's solution solved my problem. By putting quotes around the number, I am able to assign far larger values to mpz_class variables.

*SOLVED*

Member Avatar for Peter_APIIT

I don't know which one is good and need template based.

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