now if only I could remember what made me settle on those parameters...

I remember that extra flags uses in Primecoin for increase Performance or probability finding of blocks a little bit faster. But actually i never tried to understand the essence of this parameters so could be wrong. I confirm that last ver is ok, but it seems rarely finds of blocks for me. Back to previously ver.

I'll venture a hypothesis from various things I've read on this whole thread. The miner sets up the sieve, in your case 2^25 (the shift being 25) and the resultant value as the required seive size - 33554432. Now the question is how many primes to use.

All the primes chosen are (from my understanding) each multiplied by 3, then the miner starts with the highest value prime*3 and works backwards scanning for the desired gap length and not bothering with sections that obviously won't net a coin. So the largest prime value(times 3) would ideally stop just short of the end of the sieve.

So here is where a bit of math leg work comes in if you want to be precise. Absolute value of 33554432/3 is 11184810. The first prime less than that is 11184799. 11184799*3 is 33554397 which fits nicely near the top of the seive. A check of bigprimes.net shows it as the 737948th prime and thus the number of primes for shift 25.

Can someone verify if this logic is correct? I think the default primes is 500000, Maybe it could be more efficient? Also we could build a table of primes for different shift values, perhaps blocks would be found faster if everyone wasn't trying to scan 2^25 at the same time on each round.

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I calculated some surrounding shifts and will diversify my workers over them to test them out:

--sieve-size 2097152 --shift 21 --sieve-primes 56474

--sieve-size 4194304 --shift 22 --sieve-primes 106974

--sieve-size 8388608 --shift 23 --sieve-primes 203094

--sieve-size 16777216 --shift 24 --sieve-primes 386702

--sieve-size 67108864 --shift 26 --sieve-primes 1410973

--sieve-size 134217728 --shift 27 --sieve-primes 2703387