Re: [bitcoin-dev] Some real-world results about the current Segwit Discount

From: Alphonse Pace <alp.bitcoin@gmail•com>
Cc: bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Some real-world results about the current Segwit Discount
Date: Mon, 8 May 2017 18:47:32 -0500	[thread overview]
Message-ID: <CAMBsKS_j7Lso6fHoMPkrQ7UFwKfxOERAAqL=aUF83O4CqL+iFg@mail.gmail.com> (raw)
In-Reply-To: <CAKzdR-qojNn8OtUTPbxa0JauK9nmo2ZGm4ihKuyzsz_FAgokDw@mail.gmail.com>

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Sergio,

I'm not sure what the data you present has to do with the discount.  A 75%
discount prevents witness spam precisely because it is 75%, nothing more.
The current usage simply gives a guideline on how much capacity is gained
through a particular discount.  With the data you show, it would imply that
those blocks, with SegWit used where possible, would result in blocks of
~1.8MB.

On Mon, May 8, 2017 at 5:42 PM, Sergio Demian Lerner via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> I have processed 1000 blocks starting from Block #461653.
>
> I computed several metrics, including the supposed size of witness data
> and non-witness data (onchain), assuming all P2SH inputs/outputs are
> converted to P2PWSH and all P2PKH inputs/outputs are converted to P2WPKH.
>
> This takes into account that other types of transactions will not be
> modified by Segwit (e.g. OP_RETURN outputs, or P2PK). This analysis doesn't
> take into account that LN transactions may affect the current state,
>  increasing the segwit/nosegwit ratio.
>
> Among a lot of information, I've got the following real world results...
>
> acMainChainSpace =352608924
> acSegwitSpace =599400403
> Ratio segwit/nosegwit=1.6999
>
> This implies that the 75% that discount is not the best option to prevent
> witness spam in a block of 4 MB, as stated in https://segwit.org/why-a-
> discount-factor-of-4-why-not-2-or-8-bbcebe91721e.
>
> The non-witness data weight factor should not be 4 but 2.35. The closest
> integer value is 2, which leads to a 50% witness discount.
>
> The Bitcoinj source code is available for anyone to review. I encourage
> anyone to re-compute this with another utility to cross-check. Maybe
> Antoine Le Calvez (p2sh.info) would like to double-check.
>
>
>
>
>
>
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>

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