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This is why having multiple algorithms in parallel is beneficial (if done well); optimally, when an algo is stuck at high difficulty, the retarget can reduce that algo's difficulty every time a block is found on another algo for a much smoother retarget. With one algo, the difficulty retarget can only ever change the difficulty once a block is found. Which is where there are constant overshoots both ways.
Ineteresting, yes I like the myriadcoin approach. I think the difficulties of each algo there retarget independently from each other.
It's interesting that 30 blocks to retarget (at 1 block per 2 minutes) appears slow; compared to LTC or BTC this difficulty adjust is lightning fast.
At various points over the last couple years we've talked about changing the difficulty adjust and/or POW algorithm of LOG. Anything is possible if this is too annoying to deal with. A change to a myriad-like network is attractive, what do you think? Another possibility offering even more stability is moving to a merge-mined system. However it seems that our fluctuating difficulty is not really such a headache. Hop miners are still adding their hashpower to secure the network. As we grow in size these effects will be relatively smaller.
The speed of the retarget (slow or fast) really only depends on the network's hashrate compared to lone miners joining and leaving the coin. And the reason I called it slow was due to - as I said - any small miners can affect the difficulty. This was heavily increased if there were ASICs.
I personally dislike merge mining. It's a great idea on paper but most of the time the only thing that it achieves is more multipools; people mining multiple coins due to increased profits (which translates into lower coin prices) without even knowing the names of the coins they mine. But then again, I don't know any other coins using this variant of skein.
Coins like Joincoin, Digibyte, Myriad, Auroracoin are great, even considering not all of them have a "dynamic" dificulty retarget that changes the diff of stuck algos (only changes them on an individual pow basis) but it still allows for a fluid blockchain.
And - as far as I know at least - it almost completely eliminates 51% attacks (as you would need to either flashmine blocks on a single algo or dominate multiple algos, but you could make it so that a single algo can only be solved consecutively X times before a block with another algo have to be found (e.g. myriad)).
Unfortunately I don't know any disadvantages of having multiple algos but I'm sure there are some.