Hi aj,

> If you've got (A,B,C,X) where B spends A and X spends A,B,C where X+C is below fee floor while A+B and A+B+C+X are above fee floor you have the problem though.

To clarify, in this situation, I'm imagining something like

A: 0 sat, 100vB

B: 1500 sat, 100vB

C: 0 sat, 100vB

X: 500 sat, 100vB

feerate floor is 3sat/vB

With the algo:

> * is X alone above my fee rate? no, then forget it
> * otherwise, s := X.size, f := X.fees, R := [X]
> * for P = P1..Pn:
> * do I already have P? then skip to the next parent
> * s += P.size, f += P.fees, R += [P]
> * if f/s above my fee rate floor? if so, request all the txs in R

We'd erroneously ask for A+B+C+X, but really we should only take A+B.

But wouldn't A+B also be a package that was announced for B?

Please lmk if you were imagining something different. I think I may be missing something.

> Is it plausible to add the graph in?

Fun to think about. Most basic design would be to represent {spends, doesn’t spend} for a previous transaction in the package as a bit. Can think of it as a matrix where row i, column j tells you whether Tx j (directly) spends Tx i.

But of course you can omit the last row, since the child spends all of them. And since topological ordering is a requirement, you only need as many bits as there are transactions preceding this one in the package.

If you have up to 24 parents, you need 1 + 2 + ... + 23 bits to codify spending for the 2nd ... 24th parent. For a maximum 25 transactions, 23*24/2 = 276, seems like 36 bytes for a child-with-parents package. A few more for tx-with-ancestors.

Then you can split it up into sub-packages and everything. Still not sure if we really need to.

Also side note, since there are no size/count params, wondering if we should just have "version" in "sendpackages" be a bit field instead of sending a message for each version. 32 versions should be enough right?

Best,

Gloria

On Tue, 24 May 2022 at 12:48 Anthony Towns <aj@erisian.com.au> wrote:

On 23 May 2022 9:13:43 pm GMT-04:00, Gloria Zhao <gloriajzhao@gmail.com> wrote:
>> If you're asking for the package for "D", would a response telling you:
>> txid_D (500 sat, 100vB)
>> txid_A (0 sat, 100vB)
>> txid_B (2000 sat, 100 vB)
>> be better, in that case? Then the receiver can maybe do the logic
>> themselves to figure out that they already have A in their mempool
>> so it's fine, or not?
>Right, I also considered giving the fees and sizes of each transaction in
>the package in “pckginfo1”. But I don’t think that information provides
>additional meaning unless you know the exact topology, i.e. also know if
>the parents have dependency relationships between them. For instance, in
>the {A, B, D} package there, even if you have the information listed, your
>decision should be different depending on whether B spends from A.

I don't think that's true? We already know D is above our fee floor so if B with A is also above the floor, we want them all, but also if B isn't above the floor, but all of them combined are, then we also do?

If you've got (A,B,C,X) where B spends A and X spends A,B,C where X+C is below fee floor while A+B and A+B+C+X are above fee floor you have the problem though.

Is it plausible to add the graph in?

Cheers,
aj

--
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