Lets see.. Right now, we can expect a found block (whole p2pool network finds a bitcoin block) every 5 hours.
To not have any significant impact on payout, you should constantly find several shares in every round. So if you set the difficulty so that you find around 5 shares in 5 hours, you wont have much additional variance by the amount of shares you find..
Which would mean: 5 shares every 5 hours, or one share every 60 mins, which calculates to:
http://www.alloscomp.com/bitcoin/old_calculator.php<1Gh/s --> default difficulty
1Gh/s --> difficulty 1000
2Gh/s --> difficulty 2000
etc
Which would give you a share every 71 mins.
Which would give you 4 to 5 shares every block.
Easy rule of thumb, one thousand for every gigahash.
For us who actually understand the system with variance and all, this seems reasonable?
You could of course set it smaller or to default. But the actual variance you then see wouldnt go down a lot, since then the variance of the block-finding is a lot larger than the variance by share-finding.
And, also, it all is better comparable and nicer with a constant 1000 or 2000 difficulty instead of the default variable and ever changing difficulty ;-)
Ente
1 share per hour is a steep target. I wouldn't want to do that myself nor would I expect anyone else to do so.
Maybe something more like
Goal 5 shares per hour. Difficulty Target: 170 * GH/s
Goal 4 shares per hour. Difficulty Target: 210 * GH/s
Goal 3 shares per hour. Difficulty Target: 280 * GH/s
Goal 2 shares per hour. Difficulty Target: 420 * GH/s
Goal 1 shares per hour. Difficulty Target: 840 * GH/s
>5 shares per hour should be pretty low variance (most of your variances come from block time so helping network get larger is beneficial)
1 share per hour is going to be pretty hard variance.
Miners can pick a target that gives them a variance they can stomach. Everyone's treshold is different. Remember avg can be deceptive. 1/6th to 6x the average isn't that rare in the short term (say over 100 shares).
So shooting for goal of 1 share per hour means you will have some hours with 6 shares and sometimes go 6 hours (oops missed an entire block = payout) without a single share. That can be frustrating for some miners. (Total brain fart. p2pool is PPLNS so you don't need a share during a block to be paid for the block just 1 valid share in the share chain)
I will ask Meni for some better analysis (nobody knows this stuff better than him) but hopefully this provides some insight.
I was running only 1000 as my target but looking at the numbers I am going to try running at a goal of 4 shares per hour. At 12GH/s that gives me a target difficulty of 210*12 = 2500.
