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Old 2021-06-03, 13:02   #33
bsquared's Avatar
Feb 2007

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Originally Posted by charybdis View Post

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 use the following as average a,b values for norm estimates (I got these from you a few months back):
a = sqrt((double)(1ULL << (2 * I - 1)) * 1000000.0 * poly->poly->skew);
b = sqrt((double)(1ULL << (2 * I - 1)) * 1000000.0 / poly->poly->skew);

But don't take into account root properties and obviously the Q is static. If there is a better way that is nearly as simple that'd be great.

But the reason it is choosing algebraic side is that yafu is biased that way on purpose. The rational norms need to be about 5 orders of magnitude larger on the rational side before it will choose to sieve there. Can't remember why I did that... I think it's because for gnfs jobs it is usually the case where alg side is better, even when the norms are slighter higher on the rational side.

Originally Posted by charybdis View Post
@bsquared, if you're reading this - maybe worth getting YAFU to test-sieve algebraic vs rational when the estimated norms are close together?
Yes, another good idea. Should be fairly straightforward to implement.
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