Tweak PartialFactorization call when proving primality

Namely, by passing it the 'cheap' option (which implies the FactIntPartial
option), as the surrounding code would suggest. This makes calling e.g.

  IsPrimeInt(100000000000000000000000000000000000000000000000151);

with FactInt loaded almost as fast as without it loaded.

Author: fingolfin

hpcgap/lib/primality.gi

@@ -580,8 +580,8 @@ function(N)
   # try straightforward method first
   if cheap=true and FactIntPartial=true then
     to_check:=Concatenation(
-      List(Set(PartialFactorization(N-1,7)),p->["F",p]),
-      List(Set(PartialFactorization(N+1,7)),p->["L",p]));
+      List(Set(PartialFactorization(N-1,7 : cheap)),p->["F",p]),
+      List(Set(PartialFactorization(N+1,7 : cheap)),p->["L",p]));
     if [] <> PrimalityProof_VerifyStructure(N,to_check)
     then return to_check;
     else Info(InfoPrimeInt,1,"Straightforward Fermat-Lucas primality proof failed on ",N);

lib/primality.gi

@@ -580,8 +580,8 @@ function(N)
   # try straightforward method first
   if cheap=true and FactIntPartial=true then
     to_check:=Concatenation(
-      List(Set(PartialFactorization(N-1,7)),p->["F",p]),
-      List(Set(PartialFactorization(N+1,7)),p->["L",p]));
+      List(Set(PartialFactorization(N-1,7 : cheap)),p->["F",p]),
+      List(Set(PartialFactorization(N+1,7 : cheap)),p->["L",p]));
     if [] <> PrimalityProof_VerifyStructure(N,to_check)
     then return to_check;
     else Info(InfoPrimeInt,1,"Straightforward Fermat-Lucas primality proof failed on ",N);