Topic: A proposal for Recent Shared Maximum PPS - page 2. (Read 11031 times)

This is of course false, given that
1. *MPPS does not fit the goal.
2. Other systems such as PPLNS and the geometric method fit the goal.

*MPPS fit with your "real goal" much better than any other system currently.

Your mistake is assuming that the goal of a pool is to reward each share with the statistical average, exactly.

The real goal of a pool is, however, to reward each share with the statistical average, on average (while reducing variance as much as possible). On the one hand you have PPS, which is 0 variance for the miner (with maximal risk to the operator); on the other hand, solo mining which has the highest variance; and a variety of methods in between.

PS. If MPPS is what I think it is, then it is just as bad as the *SMPPS.

No matter what reward method is used, when a pool is down to zero buffer on a long round, it must either underpay or create debt for the pool owner. That is an inevitable fact of pooled mining. Nothing can stop it. *MPPS attempts to mitigate it by offering to make up for the loss later.

No matter what reward method is used, when a pool is down to zero buffer on a long round, it must either underpay or create debt for the pool owner. That is an inevitable fact of pooled mining. Nothing can stop it. *MPPS attempts to mitigate it by offering to make up for the loss later.

You are correct. This is a fundamental problem with all *MPPS pools. When the balance is negative, miners know that their payment has a good chance to be delayed. It doesn't matter if the pool pays recent first (RSMPPS), strives for equal payment for all shares (EMPPS) or pays all unsaturated shares every round (SMPPS). And, since this should quickly cause the collapse of the pool, "delayed" really means "gone forever".

Does this make sense, or am I missing something?

Recently, I've been trying to find a pool that has the most fair payout system that deters pool hopping. Slush system works ok but it's really bad for people that are not doing this 24/7. Deepbit deters pool hopping but the delayed statistics is annoying. I came across Eligius' Shared Maximum Pay Per Share (SMPPS - http://eligius.st/wiki/index.php/Shared_Maximum_PPS) model. This model works well but I believe there is a flaw. When the pool is running lucky, all is good. But when the pool is running unlucky, there is less incentives for people to join the pool because they know that they will not get their full PPS reward because a part of the earnings will need to be shared with other users that were owed rewards from previous unlucky blocks. This could potentially lead to a vicious cycle where if the difficulty increases and the pool's hashrate does not increase to match, the pool will earn less BTC and would not be able to cover the previous debt.

For example, imagine if a SMPPS pool is unlucky and currently running a 100 BTC deficit. Why would I want to join this pool? For every 1 share I contribute, I would have to likely share it with 2 others for the 50 BTC earned. Let's say the next round is an average round. The pool earns 50 BTC, but since the deficit is now 150 BTC, I will only get a third of the payout right away and need to wait for the rest… assuming I will eventually get them. So why not just join a SMPPS pool that is currently lucky? That way, I will get all the PPS rewards that I contribute. I believe this leads to pool hopping not due to long rounds, but due to lucky/unlucky pools.

I have a proposal for a better PPS system that I'm calling Recent Shared Maximum PPS or RSMPPS. The idea is simple. It's basically SMPPS, but instead of paying out the reward to all unpaid PPS proportionally, RSMPPS will favor recent blocks. So it will first proportionally pay out the unpaid PPS for the current block (the one that was just found). If there are any remaining rewards, it will pay them out to the next recent block that has unpaid PPS shares. It will keep doing that by paying out unpaid PPS shares from earlier and earlier blocks until all 50 BTC are paid out. If there are any left, it will keep those for the next unlucky round. This system will have no disadvantage for new miners joining the pool, because rewards will be first paid to the people that actually worked on the current block. So there's no debt burden on new users. And old unpaid PPS shares will get paid out if the pool gets lucky enough. With this system, it's possible for the pool to never get lucky enough to pay out really old unpaid shares. I think that's fair.

What do people think?

Vlad offers to mine for any pool for 0 variance + 10% extra with up to 50 GH/s. It would hurt any pool, yes - but most of them just for a short time: PPLNS for N shares, Prop + Scored for 1 round, pure PPS would just hurt the operator... But with *SMPPS the whole pool gets hurt for quite some time potentially.

You will get paid fully on the next block, unless it's a long round and there's no saved up buffer. In that case, you will get paid when the pool gets lucky again. In the RSMPPS case, if that never happens, you at least got paid as much as you would have if it was a proportional pool.

So are you saying Vladimir can mine at this RSMPPS pool and withhold winning shares? Basically sabotage the pool such that Vladimir will never help find the winning block. So chances are that it will lead to a long round. And miners will only get paid proportionally. In that case, it hurts Vladimir also. And why would Vladimir wanted to do that? And if someone else is paying Vladimir to do that, yes that would hurt the pool. But tell me which pool wouldn't be hurt by this withholding attack?

But if you keep mining you never know when (if?) you get paid fully. (only "eventually")

Also a serious withholding attack (can be done right now by writing a proxy and paying Vladimir to point 50 GH/s your way) will lower the reward per share significantly (down to prop.), if I got the concept right.

So if you stop mining, you know exactly how much you lose out (expected share * reward per share).

It looks like your RSMPPS is trying to take SMPPS and make it more like PPLNS. Better just use PPLNS instead.

What I don't like at both SMPPS and RSMPPS is that the pool can be in dept a lot out of a sudden bad luck streak with potentially no way to recover ever (imagine having a really bad bad luck streak at the time right before the block reward is cut in half and a lot of miners leave!)

To me PPS systems still seem to be tha fairest ones, but with SMPPS or RSMPPS there is a risk involved that some shares will never be paid, if the pool hash rate has a peak at a bad luck streak.

To me PPS systems still seem to be tha fairest ones, but with SMPPS or RSMPPS there is a risk involved that some shares will never be paid, if the pool hash rate has a peak at a bad luck streak.

Maybe I'm not getting it, but this looks to me the opposite of hopping-proof. Wait 10 days, if the pool has been lucky mine for it, if not don't.

I just wonder if/how it is a problem that PPLNS can (should!) cross block round and difficulty borders, as some shares can be (re-)considered multiple times at payouts then. I don't see any immediate exploitability though.

To me PPS systems still seem to be tha fairest ones,

Maybe something like 2-week Prop can be established, where at every difficulty change the depts/earnings get set back to 0 and all miners of this round get paid (proportionally?). Downside: You have to wait 2 weeks (or more) for your mining income and cannot get it earlier until the round is finished, no payment out of generations possible (especially tricky once the amount gets cut in half - i wonder what's eligius' strategy for this btw!). Upside: One of the fairest methods I can think of, hopping proof, easy to explain and implement, no need to patch bitcoind.

With PPLNS, variance is 0 per block for the operator and very low for the participants. Note that there is also variance created by the pool being to small regardless of the scoring method used.