http://riecoin.org/: ..
In Primecoin there is no practical way of estimating the time before finding a block, moreover difficulty 10.1 is easier than 9.9 making
it impossible to estimate how secure the network is.
This is not correct. At diff=9.9, all 10-chains found are counted as blocks. So a 10.x is always more difficult than a 9.x diff.
By the way diff a.x is more difficult than a.y f x>y, for any a as expected.
Ok, you are right that 10.x is always theoretically more difficult than 9.x. And that it may be possible to estimate the total mining power, but it really is a lot harder, and relies more on practical measurements than in theoretical models.
The thing is that the behavior is non-linear and unexpected. And because of the way miners work, in
practice it took less time to find a block at 10.1 than it did at 9.9This is because at 9.9 the miners make the sieve looking for chains of length 9 but at difficulty 10.01 they sieve for length 10. At this cirumstances, finding a block when difficulty is 10.01 is really faster than when it is 9.9.
If miners were perfect, and knew the exact value at which the sieve for 10 is more effective than the sieve for 9 then it would be different. I don't know that value but it certainly is less than 10. Using existing miners, there exists a pair of values x, y where (for the same mining power) 9.x gives blocks at the same rate than 10.y
So, Primecoiners: making the sieve for z + 1 instead of z when the difficulty is z.9 is a good miner optimization: you'll get more blocks per second. But you'll get less shorter chains/s - so it's an optimization for solo but not for pooled mining.
