Thread: NFS cofactorization with 3LP View Single Post
2020-10-19, 00:05   #3
charybdis

Apr 2020

26610 Posts

Quote:
 Originally Posted by VBCurtis I've wondered about this also, though my curiosity was about cofactors slightly bigger than 2*mfb but still too small to possibly split into 3 large primes.
CADO definitely deals with these properly - see this snippet from sieve/las-cofactor.cpp:

Code:
  nd = mpz_get_d (n);
B = (double) scs.lim;
kB = B * B;
for (klpb = lpb; klpb < s; klpb += lpb, kB *= B)
{
/* invariant: klpb = k * lpb, kB = B^(k+1) */
if (nd < kB) /* L^k < n < B^(k+1) */
return 0;
}
I couldn't find anything related to the double large prime bound, but there's a LOT of code for the siever so there's every chance I just haven't found it.