Simpler PARI/GP code than this?

[hermann@stamm-wilbrandt.de]

GIMPS mprime software creates ".proof" files for fast verification of a 
completed (long time) PRP proof/disproof.

I asked about software to verify such .proof, and @Prime95 provided 
main.c and roots.c.
The missing rootsdata.txt can be created with GP:

...
// This is a compacted table computed in pari-gp of z(p) = 
znorder(Mod(2,p)), associating for each "z" entry
// the set of primes "p" that have that z(p) value.
// The keys "z" are stored as negative values to distinguish them from 
the primes that follow each z.
int merged[] = {
#include "rootsdata.txt"
};
...

$ head rootsdata.txt && echo "..." && tail -3 rootsdata.txt
-2, 3,
-3, 7,
-4, 5,
-5, 31,
-7, 127,
-8, 17,
-9, 73,
-10, 11,
-11, 23, 89,
-12, 13,
...
-65322, 65323,
-65356, 65357,
-65370, 65371,
$


I came up with this GP script to create rootsdata.txt, verify_PRP could 
be compiled and used (generation of PRP proof for 9.4million decimal 
digit prime took 6:12h (with 16 threads), verification took only 
5:17min):

https://www.mersenneforum.org/showthread.php?p=656165&postcount=7

z(p) = znorder(Mod(2,p));
o=[List()|i<-[1..2^16]];
forprime(p=3,2^16+1,listput(~o[z(p)],p));
{
  for(i=1,2^16,if(#o[i],
    print1("-", i,",");
    foreach(o[i],x,print1(" ",x,","));
    print();
  ));
}

I feel that rootsdata.txt can be created with a much smaller GP script, 
is that true?

Regards,

Hermann.