Re: bug in PARI/GP (Segmentation Fault), please report.

[Karim Belabas <Karim.Belabas@math.u-bordeaux.fr>]

* John W. Nicholson [2014-05-25 12:55]:
[..]
> n=2;while(ln(prime(n))>ln(prime(n+1))/exp(1/(n))&&n<pl,n++);print(n)
>   ***   at top-level: ...=2;while(ln(prime(n))>ln(prime(n+1))/exp(1/(n
>   ***                                             ^--------------------
>   *** prime: bug in PARI/GP (Segmentation Fault), please report.
>   ***   Break loop: type 'break' to go back to GP prompt
> break> n
> 23163299
> break> 
> 
> Is this a bug on my machine, or can it be reproduced by others? Has this been reported before?

Can you try to narrow it down ?
With 

  n = 23163299
  N = n + 1
  alias(ln, log)

I can't reproduce it: the following command runs to completion

  while(ln(prime(n))>ln(prime(n+1))/exp(1/(n))&&n<N,n++);
Cheers,

    K.B.

P.S. Your program is inefficient: prime(n) runs in time O(n), so it runs
in time O~(N^2). Also (minor) prime(n+1) doesn't use the previously
computed prime(n). Much better:

  test(N) = 
  {
    n = 1; logprev = log(2);
    forprime(p = 3, N,
      my (l = log(p));   \\ l = log(prime(n+1)), logprev = log(prime(n))
      if (logprev*exp(1/n) <  l, print([n, p]));
      logprev = l; n++; 
    );
  }

Untested but runs in time O~(N).

--
Karim Belabas, IMB (UMR 5251)  Tel: (+33) (0)5 40 00 26 17
Universite Bordeaux 1          Fax: (+33) (0)5 40 00 69 50
351, cours de la Liberation    http://www.math.u-bordeaux1.fr/~kbelabas/
F-33405 Talence (France)       http://pari.math.u-bordeaux1.fr/  [PARI/GP]
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