Why time-based PPLNS is a BAD idea for multipool.
I know there already has been a long discussion in this thread about what payment system would be best for this type of pool and finally Flound has settled on time-based PPLNS.
I'm not trying to restart that discussion so we can hear the same arguments again and again but I have given it a lot of thought and I think I have some points that are really relevant and have not been made yet.
Flound argues that for the LTC pool 4-6 hours would be a good period to set for the time-based PPLNS. This can be fair based on his assumption that the LTC port has about 100MH on it when the multiport is on another coin.
But (for argument sake) let's look at the situation where the steady hashing power on LTC would drop to a low value or even disappear. If the multiport then moves away from LTC and doesn't return within 6 hours, it will be a FACT that all shares will be lost and the multiport miners will get nothing in return for their time spent on LTC.
So a low steady hashrate on LTC will be bad for multiport miners when using time-based PPLNS while on the other hand the 6-hour time-based PPLNS system will be unfair to the steady LTC miners when there is steady hashrate much higher than 100MH.
Based on the above, you would have to adjust the time period of the time-based PPLNS system, based on the hashing power that is on the port. Which boils down to ...... (think about it) ...... exactly the same a regular 'share based' PPLNS.
Then we have a lot of people claiming PPLNS is not suited for multipool because it was specifically designed to prevent pool hopping. While the last part is true, the multiport is not pool-hopping in a regular way.
Miners that use pool-hopping to increase their profit, hop on a pool when that pool has just found a block and starts a fresh round with 0 shares taken so far. They stay on the pool for a while but if the round is not 'lucky' and takes too long, they hop onto another pool that has just found a block and started a fresh round. PPLNS is designed to prevent this by invalidating the oldest shares on unlucky rounds.
The multiport does NOT hop onto a coin because the pool has just found a block and starts a fresh round. The multiport hops on a coin because the difficulty and/or exchange rate has changed and it became the most profitable to mine in that regard. So the point where the multipool hops into a round compared to when that round started, is absolutely random. It can be early into the round but it can just as well be at the end of a round that has been very unlucky.
For this reason, share-based PPLNS will have NO negative effects for multiport users and the effects of lucky/unlucky rounds WILL even out over time.
Actually, share-based PPLNS is even better for this type of pool than a Proportional system. With a proportional system, it could be argued that the multiport would be really 'stupid' to jump onto a coin when there is a really unlucky round going on for a long time already and many proportional shares have already been mined (unless the coin would become very profitable by a really big margin ofcourse). Share based PPLNS also evens out this effect so as far as I can see it, this is the perfect system to use on this pool.
Maybe I'm missing something here and my reasoning is flawed (I'm only human after all) so please share your thoughts if you catch something that I didn't. I'm always eager to learn.
At the end of the day it will be Flound who decides what system to use but I hope he gives this a little thought