1062

Bitcoin / Technical Support / Re: Can't Sync Bitcoin QT AND No Blockchain File on PC

on: May 04, 2013, 06:56:14 PM

20130504 11:50:03 received block 00000000000000ff4aaa342f804a2731bb9f39a784a7f1d86685b35f144cd73a 20130504 11:50:03 InvalidChainFound: invalid block=00000000000000ff4aaa342f804a2731bb9f39a784a7f1d86685b35f144cd73a height=234477 work=1131399971692442463964 date=20130504 11:47:02 20130504 11:50:03 InvalidChainFound: current best=0000000000000051e75ec922ddfed09dc3ca0a72f0e8bbc875d7b3fb370d7524 height=234410 work=1128500345104905542838 date=20130504 01:24:51
This is the crux of the problem, your local blockchain database is corrupted and the client can't build on that. It doesn't have the intelligence to try to get the block 234410 again from the network and replace your screwed up version with the correct one.
You will need to delete the blocks and chainstate directories from your bitcoin data directory and attempt to resync the blockchain from the start. Typically this kind of random corruption indicates bad hardware, such as a bad sector on a hard drive or bad math from an overheating or overclocked CPU.



1063

Other / CPU/GPU Bitcoin mining hardware / Re: How many video cards can cool 34 Kilowatt air conditioner?

on: May 04, 2013, 06:43:33 PM

The amount of heat generated by 1 kilowatt worth of computer (about four 200W video cards + system + 900W power supply inefficiency):
1kWh = 3,412 BTU
So we need 3400 BTU of A/C to remove that much heat generation.
The the next question is how much power will that cooling require. We must look at the the energy efficiency of air conditioning, which is typically given as SEER (seasonal energy efficiency ratio), which we must translate into an actual efficiency measure.
COP = 3.41214/EER
As a lowwater benchmark, lets look at a 5000 BTU window AC unit ($110 on lowes.com website) Specs: EER=9.7, Watts=515 (calculated efficiency multiplier: 2.84)
So this particular model moves 1462W of heat with 515W. A central AC will be more efficient, so 3000kW * 2.84+ = at least 8000 watts (but nothing left to actually cool your house against summer temperatures).
Real miners don't use AC though, why reduce profitability? Put the units in a closed room with a window fan, or in the garage.



1064

Other / Beginners & Help / Re: Still a little confused on Wallets.

on: May 04, 2013, 05:10:36 AM

Bitcoin gives you all you can eat addresses for free! Just put keypool=10000 in your bitcoin.conf file, now your wallet has 10,000 pregenerated addresses in it (you'll have a backup that never becomes obsolete).
There are 1461501637330902918203684832716283019655932542976 possible addresses. That's enough for 100x the world's current population to have 1826877046663628647754606040895353774 addresses each.
There will be a maximum of 2100000000000000 Bitcoin base units (a satoshi, or 0.00000001 bitcoin). Even if every single base unit that will ever be created were put in a different address, there will still be 1461501637330902918203684832716280919655932542976 empty addresses. The chance of you generating an address that has a satoshi in it will be 1 in 695953160633763294382707063198230.
So in other words, it doesn't matter if you create lots of addresses and delete them. If you never use them, the network doesn't even know they exist.



1066

Other / Meta / Re: BOOKMARK THIS SITE AS https://109.201.133.65, DOMAIN WAS TRANSFERRED

on: May 03, 2013, 10:38:58 AM

Domains get hacked often. The problem is if someone hacked the domain registrar account and transferred the domain away, it may be a bit of work to get it back. It's 7pm on a Friday in Japan, 3am in the US. It will take time through the Transfer Dispute Resolution Protocol if the receiving domain registrar doesn't immediately hand it back on the word of registrar #1.



1071

Economy / Service Discussion / Re: CoinLab suing MtGox for $75 milliion?

on: May 03, 2013, 03:01:19 AM

MtGox: we determined it was a bad idea to go through with giving this shady looking individual the banking credentials and passwords of nonconsenting users, especially since he got into the scamcoin business.
Me: Hey coinlab, where can I serve you notice? Me and 1000 others will get default judgements against your "company" in every state of the union, even before your lawsuit with MtGox is dismissed in summary judgement.



1072

Bitcoin / Development & Technical Discussion / Re: 234078 Longest block to solve yet?

on: May 03, 2013, 02:20:43 AM

It's not a bell curve, the probability density function of an exponential distribution looks like this: Note that the average block time is 10 minutes (1/λ), but 50% of the blocks are less than 6.93 minutes (the median ln(2)/λ). The reason that it makes no difference is: whether the geometric distribution (which counts individual hashes) is calculated for difficulty 1 or difficulty 10000000, the probability of a quantile (such as calculating the probability of a block taking 100 minutes) is the same within several decimal points. In fact it is already identical to the exponential (continuous) function with three digits by difficulty 1, higher difficulty just makes the density function of geometric converge to exponential with even more digits of identity. http://math.stackexchange.com/questions/93098/howdoesageometricdistributionconvergetoanexponentialdistributionHere's a monte carlo simulation of a geometric distribution density, the red line is exponential: See how much like the exponential it is? This example shows a 0.1 probability; Bitcoin's current probability is 0.0000000000000000231. With a lower probability,the steps disappear and the distribution converges to exponential. So the answer is: the probability of a block taking 62 minutes (given a constant hashrate equivalent to difficulty) is 0.2029%, whether the difficulty is 1 or a billion.



1073

Bitcoin / Development & Technical Discussion / Re: 234078 Longest block to solve yet?

on: May 02, 2013, 09:39:25 PM

My stats are a little rusty, but as far as I see, it doesn't, it goes up. Hashing is Bernoulli trial, either you beat the target or you don't. That gives mining a geometric distribution, and so the variance (in number of hashes required) is (1p)/p ^{2}. The retargeting algorithm tries to keep the hashrate directly proportional to 1/p, so the variance in time quadratically increases with the hashrate. Right? I guess the phenomenon above was a much higher variance in hashrate because of people turning their computers off at night, whereas now the variance is greatly reduced due to increased numbers and because miners tend to keep the gear running 24/7. Only 'technically', on a very small scale, is the variance different. In reality it is unobservable at different difficulties. Hashing is typically modeled as an exponential distribution, a continuous series, however it is actually a geometric distribution. The probability is so low though, that the R statistics package fails to compute due to overflow errors with statistics on much more than difficulty 1. The variance is given for a geometric distribution as: You can see that for extremely small p (probability of one hash finding a block), the top numerator approaches 1, becoming insignificant compared to the p ^{2}. The high block times around 2000030000 has something to do with the satoshi miner and others not making much hashes during that time, there was much less than difficulty 1 worth of mining being done. I could eliminate the first year of Bitcoin to get a better list of long blocks, long due to variance rather than low hashrate.



1075

Bitcoin / Development & Technical Discussion / Re: why not measure difficulty in bits?

on: May 02, 2013, 01:39:04 AM

The difficulty is actually in bits, the field in the block that contains it is called bits, which is decoded into the target. Here's the current target, a hash has to be smaller than this number: 00000000000001AA3D0000000000000000000000000000000000000000000000or in binary: 0000000000000000000000000000000000000000000000000000000110101010001111010000000 0000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000000000000000000000000000000000000 0000000000000000000 The difficulty is easy to comprehend and is what is presented to users. What you are proposing is harder: >>> math.log(2**256/ int( '00000000000001AA3D0000000000000000000000000000000000000000000000',16),2) 55.26448364017038What "bit" difficulty would be 10% harder? >>> math.log(2**256/(( int( '00000000000001AA3D0000000000000000000000000000000000000000000000',16))/ 1.10),2) 55.40198716392032Satoshi got it right. Not everyone uses Python as their calculator. Use a base difficulty, where 1 = 1 block find per ~4295032833.0 hashes on average, and higher difficulties are multipliers of that.



1079

Bitcoin / Technical Support / Re: Progress bar gone?

on: May 01, 2013, 02:08:20 PM

This could mean that you aren't connected to enough other nodes to obtain consensus about what the current best block is.
I can see by the "bars" icon that you have a limited number of node connections. This is expected if you are directly connecting to another one of your own computers using the connect option. If you are connecting to the public network, you should forward port 8333 in your Internet router to the machine running Bitcoin, or enable the option "Map port using UPnP" in Bitcoin to attempt this automatically.



1080

Bitcoin / Technical Support / Re: Old blk0001.dat, 2, 3 left over from v0.7.?

on: May 01, 2013, 02:02:53 PM

You can remove blk0001.dat, blk0002.dat, blk0003.dat and blkindex.dat from the root data directory after a reindex is complete and you are caught up with the blockchain (and you don't plan on going back to an older version). Only blkindex should actually be using disk space, as the old BLK000x data are moved upon upgrade, and the blk000x.dat files you see there are hardlinks (shortcuts) on any filesystem that supports hardlinking. The new database for v0.8.0+ is stored in two subdirectories, "blocks" (block data, with block id database in "blocks/index"), and "chainstate" (unspent output database). Do not mess with files in these subdirectories.



