I was wondering if P2Pool is decentralized why does it show up on the BitcoinWatch pool distribution graph?

I thought it would show up under "Unknown" but I guess this is only solo miners? Or some dark pool?

And "Other Known" I assume is a selection of small pools whose hash rate is too small to have a visible slice on the graph?

EDIT: It's currently not visible on the graph on BitcoinWatch but I'm certain I saw it on there not long ago so I will upload an image when I see it again.

  • The simple answer is it shows up on the pool graph because it's a pool. It doesn't matter whether it's centralised or not, it's still a group of miners pooling their mining resources and so it qualifies. Perhaps you meant to ask how it is detected, not why? – Chris Moore Feb 13 '12 at 6:02

Blockchain.info (the source of the graph) uses the "First relayed" method to attempt to determine a block's owner. The site has a database of ip addresses that belong to the major mining pools and tries to connect to each of those. If a block is received from one of those ip's first then that pool is deemed to be the owner.

For P2Pool I occasionally join the p2p network and scrape a list of "addr" messages containing the ip's of the nodes in network. These are inserted into the database under the collective "P2Pool" name.

There is actually a better way to detect P2Pool blocks as the first output of each coinbase tx is strange e.g. http://blockchain.info/block-index/857086

  • Ah I see, thanks. So p2pool users could also be in the "unknown" category as well? If they're not in your database? – Sean Chapman Jan 31 '12 at 18:28
  • Yes, I don't scrape that often so this is likely. – user418 Jan 31 '12 at 18:40
  • A better way of detecting P2Pool blocks is to check the generation transaction for the P2Pool donation address, 1Kz5QaUPDtKrj5SqW5tFkn7WZh8LmQaQi4, since every block found by P2Pool sends at least one satoshi to that address. – Chris Moore Feb 13 '12 at 6:00

All miners in P2Pool mine "solo" but distributing the reward between all its peers, hence having both advantages of solo mining and pooled mining. The reward distribution is build into the block itself, you can't mine such a block to change it later to give yourself all the reward, nor will the P2Pool accept shares that don't contain reward redistribution.

If it doesn't show as a pool it's encased into "other known".

  • This doesn't really answer my question. Sorry if it was a bit confusing. So p2pool should be falling under the "other known" category? – Sean Chapman Jan 31 '12 at 10:47

Yes, "other known" is for sources too small to show on the graph.

The graph on bitcoinwatch.com is entitled "Hashrate Distribution". If you click through to the blockchain.info site it does include the word "pool". But I think the point is just to show the major hash powers, regardless of whether they are pools. If there was a single person with enough hash power to show on the graph, I bet they'd show it, even though a single person is not a pool.

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