View Single Post
Old 2021-06-02, 23:04   #30
charybdis's Avatar
Apr 2020

1111011012 Posts

Originally Posted by bur View Post
I tried 2^528 with yafu settings and the sieving had an ETA of about 3 h if I chose tasks.sieve.sqside = 1 as per EdH's guide. I switched to tasks.sieve.sqside = 0 and ETA changed to 1 h. I also changed lim0/1 to 4500000 instead of yafu's 6100000 (yes, never change more than one parameter when testing), but I guess the sqside=0 is the big impact?

Would it be advisable to generally use yafu's settings but with tasks.sieve.sqside = 0?
I don't know how you got such a huge difference in the ETAs; CADO can spit out some suspect values early on in the job, and I bet that if you let these jobs run to completion the running times would be much closer. I did some test-sieving on this number with YAFU's choice of polynomial and params, and tasks.sieve.sqside = 0, ie rational side sieving, is definitely faster - but not by anywhere near that much. The advantage is larger at smaller Q values and I reckon it would amount to ~15% over the whole job.

I calculated the norms for a few relations around Q=2M, and typical values are something like 10^36 for the algebraic norm and 10^39 for the rational norm. This is consistent with a small advantage for rational-side sieving. YAFU's estimates weren't too far off, but it overestimated the algebraic norm and so it chose the algebraic side for sieving.

I'd say keep on using tasks.sieve.sqside = 0 for these jobs, as it's likely that YAFU is systematically overestimating the algebraic norm. The advantage for the rational side should grow as the numbers get larger, until you switch to degree 6 at which point the algebraic side may be worth considering again.

@bsquared, if you're reading this - maybe worth getting YAFU to test-sieve algebraic vs rational when the estimated norms are close together?

Last fiddled with by charybdis on 2021-06-02 at 23:05
charybdis is offline   Reply With Quote