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In this forum post the poster (2112) writes:

It is my understanding that at least Eligius pool isn't a "honest node" and intentionally produces acausal blocks (or at least as close to acausal as they deem practical).

What is an acausal block? Or at least what did the poster mean by "acausal block". From reading the thread I get some idea that it is something to do with messing with the timestamp of the block but don't really understand it.

Perhaps this should be a separate question but does the block miner determine the timestamp that is recorded in that block?

Community
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kirian
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2 Answers2

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It allows the pool to avoid making new work for every single request. Instead, it just increments the time by a second and gives that to the next miner. Under heavy load (longpolls), Eligius might use the same work for up to 7,200 miners, meaning the last miner gets a work timestamped 2 hours into the future. This helps reduce stale shares significantly.

Luke-Jr
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He's talking about blocks with timestamps before the previous block.

Miners do determine the timestamp, though it has to be within a certain range. See: https://en.bitcoin.it/wiki/Block_timestamp

theymos
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    is there some advantage to be gained by the miner from doing this? or is it just a case of the miners clock being inaccurate? – kirian Oct 13 '11 at 21:05
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    Pools with Roll-NTime like Eligius allow their miners to change the time a little. The time is then used as an extra nonce. This can be desirable for pools/miners. Acausal time can also happen when a node with a too-slow clock solves a block, or when the network corrects after a node with a too-fast clock solves a block. – theymos Oct 14 '11 at 02:10