[bbwjsktd] Benchmarking modular exponentiation of Pari/GP

Some benchmarking of modular exponentiation for Cullen primes. Times are in milliseconds.

model name      : Intel(R) Core(TM)2 Duo CPU     P7570  @ 2.26GHz

 GP/PARI CALCULATOR Version 2.5.0 (released)
 i686 running linux (ix86/GMP-5.0.1 kernel) 32-bit version
 compiled: Sep  4 2011, gcc-4.6.1 (Ubuntu/Linaro 4.6.1-7ubuntu2)

? allocatemem(6*10^8)
  ***   Warning: new stack size = 600000000 (572.205 Mbytes).

? gettime;for(i=1,15,c=cullen[i];p=1+c*2^c;print(Mod(1,p)==Mod(2,p)^((p-1)/2));print(c," ",gettime))
1
141 0
1
4713 244
1
5795 429
1
6611 576
1
18496 6953
1
32292 27149
1
32469 27374
1
59656 119627
1
90825 333105
1
262419 3532668
1
361275 6784853
1
481899 11800874
1
1354828 113855267

Final entry is 1.3 days. Going by roughly quadratic growth, the next exponent 6328548 will take 30 to 40 days.