1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
Received: from sog-mx-2.v43.ch3.sourceforge.com ([172.29.43.192]
helo=mx.sourceforge.net)
by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76)
(envelope-from <thomasv@electrum.org>) id 1YrZIf-0007YI-8A
for bitcoin-development@lists.sourceforge.net;
Sun, 10 May 2015 22:02:17 +0000
X-ACL-Warn:
Received: from slow1-d.mail.gandi.net ([217.70.178.86])
by sog-mx-2.v43.ch3.sourceforge.com with esmtp (Exim 4.76)
id 1YrZIe-00056g-0z for bitcoin-development@lists.sourceforge.net;
Sun, 10 May 2015 22:02:17 +0000
Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net
[217.70.183.198])
by slow1-d.mail.gandi.net (Postfix) with ESMTP id 9CDFB47B8BC
for <bitcoin-development@lists.sourceforge.net>;
Sun, 10 May 2015 23:48:49 +0200 (CEST)
Received: from mfilter8-d.gandi.net (mfilter8-d.gandi.net [217.70.178.137])
by relay6-d.mail.gandi.net (Postfix) with ESMTP id 13749FB86F
for <bitcoin-development@lists.sourceforge.net>;
Sun, 10 May 2015 23:48:41 +0200 (CEST)
X-Virus-Scanned: Debian amavisd-new at mfilter8-d.gandi.net
Received: from relay6-d.mail.gandi.net ([217.70.183.198])
by mfilter8-d.gandi.net (mfilter8-d.gandi.net [10.0.15.180])
(amavisd-new, port 10024) with ESMTP id E8pGbEpph-84
for <bitcoin-development@lists.sourceforge.net>;
Sun, 10 May 2015 23:48:39 +0200 (CEST)
X-Originating-IP: 92.229.161.198
Received: from [192.168.1.2] (x5ce5a1c6.dyn.telefonica.de [92.229.161.198])
(Authenticated sender: thomasv@electrum.org)
by relay6-d.mail.gandi.net (Postfix) with ESMTPSA id 9FCECFB8A0
for <bitcoin-development@lists.sourceforge.net>;
Sun, 10 May 2015 23:48:39 +0200 (CEST)
Message-ID: <554FD237.2020009@electrum.org>
Date: Sun, 10 May 2015 23:48:39 +0200
From: Thomas Voegtlin <thomasv@electrum.org>
User-Agent: Mozilla/5.0 (X11; Linux x86_64;
rv:31.0) Gecko/20100101 Thunderbird/31.6.0
MIME-Version: 1.0
To: bitcoin-development@lists.sourceforge.net
References: <16096345.A1MpJQQkRW@crushinator>
<CAOG=w-szbLgc1jLpkE_uMa3bkFTi-RiBEaQ6Y-u5aKLBC2HvUg@mail.gmail.com>
In-Reply-To: <CAOG=w-szbLgc1jLpkE_uMa3bkFTi-RiBEaQ6Y-u5aKLBC2HvUg@mail.gmail.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: quoted-printable
X-Spam-Score: 0.0 (/)
X-Spam-Report: Spam Filtering performed by mx.sourceforge.net.
See http://spamassassin.org/tag/ for more details.
X-Headers-End: 1YrZIe-00056g-0z
Subject: Re: [Bitcoin-development] Proposed alternatives to the 20MB step
function
X-BeenThere: bitcoin-development@lists.sourceforge.net
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: <bitcoin-development.lists.sourceforge.net>
List-Unsubscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
<mailto:bitcoin-development-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development>
List-Post: <mailto:bitcoin-development@lists.sourceforge.net>
List-Help: <mailto:bitcoin-development-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/bitcoin-development>,
<mailto:bitcoin-development-request@lists.sourceforge.net?subject=subscribe>
X-List-Received-Date: Sun, 10 May 2015 22:02:17 -0000
Le 08/05/2015 22:33, Mark Friedenbach a =E9crit :
> * For each block, the miner is allowed to select a different difficul=
ty
> (nBits) within a certain range, e.g. +/- 25% of the expected difficulty=
,
> and this miner-selected difficulty is used for the proof of work check.=
In
> addition to adjusting the hashcash target, selecting a different diffic=
ulty
> also raises or lowers the maximum block size for that block by a functi=
on
> of the difference in difficulty. So increasing the difficulty of the bl=
ock
> by an additional 25% raises the block limit for that block from 100% of=
the
> current limit to 125%, and lowering the difficulty by 10% would also lo=
wer
> the maximum block size for that block from 100% to 90% of the current
> limit. For simplicity I will assume a linear identity transform as the
> function, but a quadratic or other function with compounding marginal c=
ost
> may be preferred.
>=20
Sorry but I fail to see how a linear identity transform between block
size and difficulty would work.
The miner's reward for finding a block is the sum of subsidy and fees:
R =3D S + F
The probability that the miner will find a block over a time interval is
inversely proportional to the difficulty D:
P =3D K / D
where K is a constant that depends on the miner's hashrate. The expected
reward of the miner is:
E =3D P * R
Consider that the miner chooses a new difficulty:
D' =3D D(1 + x).
With a linear identity transform between block size and difficulty, the
miner will be allowed to collect fees from a block of size: S'=3DS(1+x)
In the best case, collected will be proportional to block size:
F' =3D F(1+x)
Thus we get:
E' =3D P' * R' =3D K/(D(1+x)) * (S + F(1+x))
E' =3D E - x/(1+x) * S * K / D
So with this linear identity transform, increasing block size never
increases the miners gain. As long as the subsidy exists, the best
strategy for miners is to reduce block size (i.e. to choose x<0).
|
