P-1 factorer

[garo]

It's an original factor - didn't find it in the latest files posted by Louie and the n was listed as uncleared in one of the lists posted recently.

It took me about 5 hours on an Athlon 1333 with bounds of 25000 2500000. Looking at the factorization of P-1 one can see that bounds of 6000 and 160000 would have sufficed.

961094450858074349 -1 = 2 ^ 2 x 47 ^ 2 x 61 x 2243 x 5107 x 155663

I looked at how much P-1 has been done on the numbers in the 4million range in GIMPS and how much the client currently tries to P-1 on a P4. Here is the result:

If the number is not tested and has been trial factored to 62 bits:
B1= 45,000 B2=753750

If it has been factored to 63 bits the bounds drop to

B1=40000 B2=640000

If it has already been tested once, ie in the doublecheck phase:

B1=20,000 B2=260,000


So, looks like biwema's estimate of keeping B2 about 10-25 times B1 seems to be correct as is his suggestion of raising B1. I'd suggest 50,000 and 1 million as reasonable bounds unless someone does an analysis.

[Edit: If we consider the fact that sieving has only reached 2^45 whereas GIMPS factors these numbers to 2^61, maybe raising B1 even more might be useful. But then we also have to consider the fact that GIMPS factors have a special form so their bounds can afford to be a little higher.]