memory requirements?

[Sisyphus]

Johan ... wrote:
> Hi
> 
> I downloaded the gmp package today and compiled everything. After I compiled the 
> calculator demo and tried some numbers I noticed that trying to calculate the 
> 40th known mersenne prime, which is 2^20996011 - 1, caused the program to crash. 
> Everything else works nice and smooth though
> 
> Is this some sort of memory issue or is it something else? ...and in that case, 
> how can I make it work. Btw.. I've got 512mb ram on my win xp computer.
> 
> ..and the 40th mersenne prime has 6.3 * 10^6 digits.
> 

The following works fine for me (Linux, with 256 megs of ram):

#include <stdio.h>
#include <gmp.h>

int main() {
   mpz_t m;

   mpz_init2(m, 20996012);

   mpz_setbit(m, 20996011);
   mpz_sub_ui(m, m, 1);

   mpz_out_str(NULL, 16, m);

   printf("\n");

return 0;
}

However, if I change the output base from 16 to 10, then I get a 
segmentation fault when I run the executable. I assume this is a result 
of the increased memory requirements needed to convert from binary to 
decimal.
My guess is that you're getting a pop-up complaining about an "unknown 
software exception".

Cheers,
Rob