mersenneforum.org Polynomial selection for 2,2246M c221
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2021-12-20, 23:07   #34
charybdis

Apr 2020

17×41 Posts

Quote:
 Originally Posted by Gimarel I think, that the parameters for cado have to be reconsidered. For about 16h I run Code: polyselect -d 6 -n 24023387191766184217094927222587025087468868508838209688355658860897738047963529318736265313199625192712082581481439831563094403250831892547179972207284600405234081309183045488404642574713121441527058807512178264038863337 -P 5000000 -admin 1260 -admax 126001 -incr 420 -sopteffort 1 -t 32 -v -nq 279936 This isn't complete yet. Running msieve rootsieve on the resulting size-optimized polys gives a best score 3.097e-16. Cados ropt with ropteffort 1 gets a score 2.875e-16 on the same size-optimized poly but ropteffort 10 gets only 2.760e-16.
Turns out this is not a bug, it's just unlucky. Running with -ropteffort 1 will not be better in general.

Quote:
 Originally Posted by Shi Bai I think this is not totally unexpected. The quick answer is the candidate polynomial got discarded during the test root sieve procedure. For convenience, I will denote the polynomial generated from "-ropteffort 1: 2.026e-09" as the "BestPoly". The ropt code starts with generating many sublattices of linear rotation of the form (a, b) (mod M) where M is a product of small prime powers. They denote f + (a*x + b)*g. The best sublattices are recorded in a global queue using the rough E-score (this is lognorm + alpha). Then it starts some short test root sieve on these (a, b) (mod M) to filter out some good (a, b) (mod M) in terms of MurphyE-score. Note there will be some discrepancies between the E-score and MurphyE-score, e.g. good polynomials with E-score may have worse MurphyE-score during the test root sieve. The BestPoly was generated by a rotation of (-159023*x - 1150894624933)*g(x) + f(x) from the original polynomial f(x), g(x), together with some minor size-optimization in the end. For such rotation, it sits on the sublattice: # Info: tune [ 363], E: 55.36, lat (0, 506257, 523547) (mod 665280) This sublattice is found in both cases (ropt = 1 and/or 10). However, when ropt = 10, there are many sublattice candidates whose MurphyE score is better than this BestPoly (during the test root sieve). Thus the sublattice for this BestPoly was discarded (before entering the actual root sieve) when ropt = 10.

 2021-12-20, 23:38 #35 EdH     "Ed Hall" Dec 2009 Adirondack Mtns 2×2,251 Posts i wonder if this explains why my spin script sometimes loses the best scoring poly I start with. . .
2021-12-21, 13:07   #36
swellman

Jun 2012

13×269 Posts

Quote:
 Originally Posted by VBCurtis There's no harm in waiting for your last run, but I can say I won't be giving this a shot after all- that "4" is plenty to declare victory and move to test-sieving. If Greg would like someone else to test-sieve for him, I can take it on this week.
My last CADO run finished with a 2.8 handle, so nowhere near Gimarel’s top poly. I have finished searching.

Onward!

2022-01-16, 16:22   #37
swellman

Jun 2012

DA916 Posts

Quote:
 Originally Posted by VBCurtis There's no harm in waiting for your last run, but I can say I won't be giving this a shot after all- that "4" is plenty to declare victory and move to test-sieving. If Greg would like someone else to test-sieve for him, I can take it on this week.
Bump. Are you still willing to test sieve this? Assuming of course that Greg is still willing to sieve it.

 2022-01-16, 18:29 #38 VBCurtis     "Curtis" Feb 2005 Riverside, CA 22·1,319 Posts Ya, sure- I'll have time sometime this week.

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