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From: Jonathan Toomim <j@toom.im>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: [bitcoin-dev] Composite priority: combining fees and bitcoin-days into one number
Date: Tue, 27 Oct 2015 21:26:52 -0700	[thread overview]
Message-ID: <291B85A6-D8D4-443B-B03B-C675CBEEC662@toom.im> (raw)

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Assigning 5% of block space based on bitcoin-days destroyed (BDD) and the other 95% based on fees seems like a rather awkward approach to me. For one thing, it means two code paths in pretty much every procedure dealing with a constrained resource (e.g. mempool, CNB). This makes code harder two write, harder to maintain, and slower to execute. As a result, some people have proposed eliminating BDD priority altogether. I have another idea.

We can create and maintain a conversion rate between BDD and fees to create a composite priority metric. Then we just do compPrio = BDD * conversionRate + txFee.

How do we calculate conversionRate? We want the following equation to be true:

sum(fees) = sum(BDD) * conversionRate * BDDweight

So we sum up the mempool fees, and we sum up the mempool BDD. We get a policy statement from the command line for a relative weight of BDD vs fees (default 0.05), and then conversionRate = (summedFees / summedBDD) * BDDWeight.

As an optimization, rather than scanning over the whole mempool to calculate this, we can just store the sum and add or subtract from it each time a tx enters or leaves the mempool. In order to minimize drift (the BDD for a transaction changes over time), we recalculate the whole thing each time a new block is found.

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             reply	other threads:[~2015-10-28  4:26 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-10-28  4:26 Jonathan Toomim [this message]
2015-10-28  7:13 ` [bitcoin-dev] Composite priority: combining fees and bitcoin-days into one number Luke Dashjr
2015-10-28 22:41   ` Jonathan Toomim
2015-10-29  0:55     ` Luke Dashjr

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