From: Tier Nolan <tier.nolan@gmail•com>
Cc: bitcoin-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] Why not Child-Pays-For-Parent?
Date: Fri, 10 Jul 2015 17:28:02 +0100 [thread overview]
Message-ID: <CAE-z3OV+-18VLbOfWzDnE5HWJ4436HGtC_qDFFVkFQTGyjGOVw@mail.gmail.com> (raw)
In-Reply-To: <6D3AACE5-D6CD-4785-8A55-F6DF0B94D927@ricmoo.com>
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On Fri, Jul 10, 2015 at 5:09 PM, Richard Moore <me@ricmoo•com> wrote:
> I was also wondering, with CPFP, should the transaction fee be based on
> total transactions size, or the sum of each transaction’s required fee? For
> example, a third transaction C whose unconfirmed utxo from transaction B
> has an unconfirmed utxo in transaction A (all of A’s inputs are confirmed),
> with each A, B and C being ~300bytes, should C’s transaction fee be 0.0001
> btc for the ~1kb it is about to commit to the blockchain, or 0.0003 btc for
> the 3 transactions it is going to commit.
>
It should be whatever gives the highest fee. In effect, child pays for
parent creates compound transactions.
A: 250 bytes, 0 fee
B: 300 bytes: 0.0005 fee
C: 400 bytes: 0.0001 fee
There are 3 combinations to consider
A: 0 fee for 250 bytes = 0 per byte
A&B: 0.0005 fee for 550 bytes = 0.91 uBTC per byte
A&B&C: 0.0006 fee for 950 bytes = 0.63uBTC per byte
This means that the A&B combination has the best fee per byte value. A&B
should be added to the memory pool (if 0.91 uBTC per byte is above the
threshold).
Once A&B are added, then C can be reconsidered on its own.
C: 0.0001 for 400 bytes = 0.25 BTC per byte
If that is above the threshold, then C should be added.
In practice, it isn't possible to check every combination. If there are N
transactions, then checking all triple combinations costs around N cubed.
A 2 pass system could get a reasonably efficient result.
B is 0.0005 fee for 300 bytes = 1.67 uBTC per byte and is assumed to be a
high value transaction.
The algorithm would be
Pass 1:
Process all transactions in order of BTC per byte, until block is full
If the transaction's parents are either already in the pool or a
previous block, add the transaction.
Pass 1:
Process all non-included transactions in order of BTC per byte, until block
is full
If the transaction's parents are either already in the pool or a
previous block, add the transaction.
Otherwise, consider the transaction plus all non-included ancestors as
a single transaction
If this combined transaction has a higher BTC per byte than the
lowest transaction(s),
add the combined transaction
drop the other transaction(s)
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next prev parent reply other threads:[~2015-07-10 16:28 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-10 16:09 Richard Moore
2015-07-10 16:13 ` Jeff Garzik
2015-07-10 16:25 ` Richard Moore
2015-07-10 16:26 ` Dan Bryant
2015-07-10 16:28 ` Tier Nolan [this message]
2015-07-10 16:31 ` Jeff Garzik
2015-07-10 17:02 ` Justus Ranvier
2015-07-10 17:16 ` Dan Bryant
2015-07-10 17:51 ` Alex Morcos
2015-07-10 19:39 ` Tier Nolan
2015-07-10 21:10 ` Luke Dashjr
2015-07-11 20:28 ` Micha Bailey
2015-07-11 21:30 ` Dan Bryant
2015-07-11 22:29 ` Jeff Garzik
2015-07-12 10:18 ` Matt Whitlock
2015-07-11 23:19 ` Tier Nolan
2015-07-10 17:28 ` Tier Nolan
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