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From: Jeff Garzik <jgarzik@gmail.com>
To: 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 12:31:01 -0400	[thread overview]
Message-ID: <CADm_WcYQLzqQLY-Dspd1jUtF9Z=_721TReoc_eKYk5JCQ4fejg@mail.gmail.com> (raw)
In-Reply-To: <CAE-z3OV+-18VLbOfWzDnE5HWJ4436HGtC_qDFFVkFQTGyjGOVw@mail.gmail.com>

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This is a good explanation but it does not address reachability.  TX_a, the
first tx sent out on the network, presumably has insufficient fee to get
mined - which also means it did not necessarily even reach all miners.

Simply sending out TX_b with added fee does not guarantee that nodes
suddenly have TX_a, which they may have ignored/dropped before.



On Fri, Jul 10, 2015 at 12:28 PM, Tier Nolan <tier.nolan@gmail.com> wrote:

>
>
> 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)
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>

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  reply	other threads:[~2015-07-10 16:31 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-10 16:09 [bitcoin-dev] Why not Child-Pays-For-Parent? 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
2015-07-10 16:31   ` Jeff Garzik [this message]
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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