Quote from: jothan on May 31, 2012, 06:43:18 PM

I have seen you use that expression before, but I have never seen you explain it.

That's because I was never asked Wink

Shift-PPLNS is a method invented by DrHaribo of BitMinter which I then refined a bit. I've discussed it briefly in this comment as well as section "PPLNS variants" of AoBPMRS.

Shift here refers not to bit-shift, rather to worker shifts. Shares are grouped into shifts, and miners are rewarded for the shares they submitted in last few shifts rather than the last N shares. Since all shares submitted within a shift are equivalent, there's no need to store the individual shares, rather just the total shares submitted per miner per shift (or more accurately the total pB).

By using a gap of 1 shift between work and reward, it also doesn't matter (on average) whether a share is counted as belonging to one shift or the next. So this works in parallel - each pool instance tallies work per shift for the miners connected to it (because of the gap, it is ok to be a little out of sync with the other instances wrt which is the current shift) and then compute rewards after the fact with the summed data.

Shift-DGM is applying the same principles to DGM. I've never actually worked out the details (again, due to lack of interest), but it should work. The idea is that shares will decay only between shifts rather than within a shift, so you can do it in parallel with out-of-sync instances. Within a shift it's a simple tally of the total pB of shares submitted.