rich1.0James O'Beirne [ARCHIVE] (npub1dp…ymz3t)https://yabu.me/npub1dpdfw74plzm03mzglkdegp3hqn6qs9yffqefa5kh98mru49nrg7szymz3tnjumphttps://yabu.me📅 Original date posted:2022-02-17 📝 Original message:> Is it really true that miners do/should care about that? De facto, any miner running an unmodified version of bitcoind doesn't care about anything aside from ancestor fee rate, given that the BlockAssembler as-written orders transactions for inclusion by descending ancestor fee-rate and then greedily adds them to the block template. [0] If anyone has any indication that there are miners running forks of bitcoind that change this behavior, I'd be curious to know it. Along the lines of what AJ wrote, optimal transaction selection is NP-hard (knapsack problem). Any time that a miner spends deciding how to assemble the next block is time not spent grinding on the nonce, and so I'm skeptical that miners in practice are currently doing anything that isn't fast and simple like the default implementation: sorting fee-rate in descending order and then greedily packing. But it would be interesting to hear evidence to the contrary. --- You can make the argument that transaction selection is just a function of mempool contents, and so mempool maintenance criteria might be the thing to look at. Mempool acceptance is gated based on a minimum feerate[1]. Mempool eviction (when running low on space) happens on the basis of max(self_feerate, descendant_feerate) [2]. So even in the mempool we're still talking in terms of fee rates, not absolute fees. That presents us with the "is/ought" problem: just because the mempool *is* currently gating only on fee rate doesn't mean that's optimal. But if the whole point of the mempool is to hold transactions that will be mined, and if there's good reason that txns are chosen for mining based on fee rate (it's quick and good enough), then it seems like fee rate is the approximation that should ultimately prevail for txn replacement. [0]: https://github.com/bitcoin/bitcoin/blob/master/src/node/miner.cpp#L310-L320 [1]: https://github.com/bitcoin/bitcoin/blob/master/src/txmempool.cpp#L1106 [2]: https://github.com/bitcoin/bitcoin/blob/master/src/txmempool.cpp#L1138-L1144 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20220217/178b279c/attachment.html>