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From: Tamas Blummer <tamas.blummer@gmail.com>
In-Reply-To: <7E4FA664-BBAF-421F-8C37-D7CE3AA5310A@gmail.com>
Date: Mon, 28 May 2018 20:28:16 +0200
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To: Jim Posen <jim.posen@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 158 Flexibility and Filter Size
Precedence: list

Forgot to mention: The link I sent is to a branch that is patched to =
produce the filter stats.=20
This is the main project and the BIP158 implementation: =
https://github.com/rust-bitcoin/rust-bitcoin-spv/blob/master/src/blockfilt=
er.rs

Tamas Blummer

> On May 28, 2018, at 20:18, Tamas Blummer <tamas.blummer@gmail.com> =
wrote:
>=20
> Hi Jim,
>=20
> A =E2=80=9Cbasic=E2=80=9D combined filter would mean up to 0.5 GB =
filter data per month (with 100% segwith use). Considering that 1 GB is =
the usual data quota for an entry level mobile phone contract, this =
could be a too high barrier for adoption.
>=20
> I repeated your calculations and produced a slightly different graph =
that shows the fraction of cummulative filter size to cummulative =
blockchain size. This is less noisy but otherwise confirms your =
measurement.
>=20
> I think that the data supports separation of filters as a combined =
filter does not seem to come with significant savings. (basic  size ~=3D =
txid + input points + output scripts sizes)
> =20
> My calculations are repeatable with:
>=20
> =
https://github.com/tamasblummer/rust-bitcoin-spv/blob/blockfilterstats/src=
/bin/blockfilterstats.rs
>=20
> that is using a Rust implementation of an SPV client built on top of =
other libraries we work on in the rust-bitcoin GitHub community =
(https://github.com/rust-bitcoin). Yes, this is a shameles plug for the =
project hoping to attract more developer.
>=20
> Tamas Blummer
>=20
>=20
> <filters.png>
>=20
>> On May 24, 2018, at 05:48, Jim Posen via bitcoin-dev =
<bitcoin-dev@lists.linuxfoundation.org> wrote:
>>=20
>> Greg, I've attached a graph including the input scripts.
>>=20
>> In the top graph, we can see how the input script filter compares to =
the input outpoint filter. It is definitely smaller as a result of =
address reuse. The bottom graph shows the ratio over time of combining =
the input prev script and output script filters vs keeping them =
separate. In more recent blocks, it appears that there are decreasing =
savings.
>>=20
>=20