Proof-of-work difficulty increasing - page 2.

Bitcoiner

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Quote from: knightmb on July 16, 2010, 01:33:57 PM

Quote from: satoshi on July 16, 2010, 01:29:28 PM

Yes, about 20 hours. (120 conf / 6 blocks per hour = 20 hours) That's the normal length of time before you can spend it. You'll know long before that that you won one.

So if the difficulty was increased so high that it took a day to find a winning block, that means the lucky winner would have to wait 120 day before they could spend it or about 4 months if everyone else was averaging about the same speed? Seems like at the high end of the difficulty, there is an issue with coin generation vs. being able to put it into circulation by spending. Wouldn't the long delay cause a lot of generated coin to be lost because anything could happen to the PC that won in a long amount of time if the winner had to really wait that long? They might un-install the program or the computer get eaten by a virus or power surge well before then.

I think that the overall network is generating the same amount of blocks regardless of the difficulty; the difficulty is intended so that the network generates a block in a relatively constant amount of time. Therefore, this confirmation time should always be around the same.

Satoshi or anyone else can correct me if I'm wrong

knightmb

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Quote from: satoshi on July 16, 2010, 01:29:28 PM

Yes, about 20 hours. (120 conf / 6 blocks per hour = 20 hours) That's the normal length of time before you can spend it. You'll know long before that that you won one.

So if the difficulty was increased so high that it took a day to find a winning block, that means the lucky winner would have to wait 120 day before they could spend it or about 4 months if everyone else was averaging about the same speed? Seems like at the high end of the difficulty, there is an issue with coin generation vs. being able to put it into circulation by spending. Wouldn't the long delay cause a lot of generated coin to be lost because anything could happen to the PC that won in a long amount of time if the winner had to really wait that long? They might un-install the program or the computer get eaten by a virus or power surge well before then.

satoshi

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Yes, about 20 hours. (120 conf / 6 blocks per hour = 20 hours) That's the normal length of time before you can spend it. You know long before that that you won one.

knightmb

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Quote from: satoshi on July 16, 2010, 12:56:54 PM

It adjusted to 181.54 a few minutes ago. Typical time to get a block is about a week now.

The difficulty can adjust down as well as up.

The network should be generating close to 6 blocks per hour now.

Yeah, I've noticed the "10 second blocks" are gone, replaced with 419 and 741 second block generation with no more in the last 20 minutes. That should keep those server farms on hold for a while Wink

Now, correct me if I'm wrong, but now that block generation is taking a lot longer, doesn't that mean that the lucky person who got the block is going to take a lot longer to be verified by the network that he/she was the winner before they could ever spend it?

RudeDude

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Quote from: gould on July 13, 2010, 05:30:59 PM

I'd be interested in seeing something like "expected bitcoins generated/day" next to (or in place of) the khash/s number. I'd rarely need to see the khash/s number since that won't change unless I make changes to the software or hardware.

I think the web c alc does a good job by showing likelyhoods based on khash speed:
http://www.alloscomp.com/bitcoin/calculator.php

That way you can see there is no guaranteed time horizon.

satoshi

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It adjusted to 181.54 a few minutes ago. Typical time to get a block is about a week now.

The difficulty can adjust down as well as up.

The network should be generating close to 6 blocks per hour now.

knightmb

sr. member

Activity: 308

Merit: 256

Quote from: Bitcoiner on July 16, 2010, 10:48:54 AM

Quote from: satoshi on July 16, 2010, 10:46:12 AM

The proof-of-work difficulty is currently 45.38. (see http://www.alloscomp.com/bitcoin/calculator.php)

It's about to increase again in a few hours. It's only been 3-4 days since the last increase, so I expect it will increase by the max of 4 times, or very nearly the max. That would put it at 181.54.

The target time between adjustments is 14 days, 14/3.5 days = 4.0 times increase.

Holy....

Satoshi, what happens if the rush dries up for a bit; some of the slashdotters or whoever get tired? Does the difficulty ever go back down?

If I'm reading the source code correctly, it should go up and down based on how much CPU is being thrown at it. So if someone rented a super computer to drive up the difficulty for a week, then it vanished, the difficulty should float back down.

Bitcoiner

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Quote from: satoshi on July 16, 2010, 10:46:12 AM

The proof-of-work difficulty is currently 45.38. (see http://www.alloscomp.com/bitcoin/calculator.php)

It's about to increase again in a few hours. It's only been 3-4 days since the last increase, so I expect it will increase by the max of 4 times, or very nearly the max. That would put it at 181.54.

The target time between adjustments is 14 days, 14/3.5 days = 4.0 times increase.

Holy....

Satoshi, what happens if the rush dries up for a bit; some of the slashdotters or whoever get tired? Does the difficulty ever go back down?

satoshi

founder

Activity: 364

Merit: 6472

The proof-of-work difficulty is currently 45.38. (see http://www.alloscomp.com/bitcoin/calculator.php)

It's about to increase again in a few hours. It's only been 3-4 days since the last increase, so I expect it will increase by the max of 4 times, or very nearly the max. That would put it at 181.54.

The target time between adjustments is 14 days, 14/3.5 days = 4.0 times increase.

Insti

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Activity: 294

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Firstbits: 1duzy

13/07/2010 0000000005a3f437d4a7f529fd4a7f529fd4a7f529fd4a7f529fd4a7f529fd4a

Insti

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Firstbits: 1duzy

Quote from: gould on July 13, 2010, 05:30:59 PM

I'd be interested in seeing something like "expected bitcoins generated/day" next to (or in place of) the khash/s number. I'd rarely need to see the khash/s number since that won't change unless I make changes to the software or hardware.

You can use the calculator at: http://www.alloscomp.com/bitcoin/calculator.php

If this is a feature request post in the Development & Technical Discussion Forum: http://bitcointalk.org/index.php?board=6.0

gould

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I'd be interested in seeing something like "expected bitcoins generated/day" next to (or in place of) the khash/s number. I'd rarely need to see the khash/s number since that won't change unless I make changes to the software or hardware.

theymos

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The probability of winning per hash went from 9.90701E-12 to 5.12995E-12. So about double the difficulty.

laszlo

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"difficulty" : 45.38582234101263

It jumped from 23 in a couple days. I think this pretty much puts an end to generating a block a day with a personal computer.. but you can still get lucky. Now you'll need to build a cluster or hijack a college computer lab for it to be worth doing

I expect the trading value will increase significantly over the next few weeks as the supply slows down; should be interesting.

satoshi

founder

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Agree. Certainly too trivial to clutter the user's attention with.

I changed it to every 30 minutes.

If I increased it to every 10 minutes, it would still be a small enough presence in the log file. Question is whether that would be more output than the user wants when they grep.

Gavin Andresen

legendary

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Chief Scientist

Quote from: ?? on ??

How about in the options menu you can turn it off or on, and specify an interval in minutes for how often it should display?

I say keep it simple; more choices isn't always better, it just makes it overwhelming and confusing for most users.

satoshi

founder

Activity: 364

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I integrated the hashmeter idea into the SVN version. It displays khash/s in the left section of the status bar.

Two new log messages:
21/06/2010 01:23 hashmeter 2 CPUs 799 khash/s
21/06/2010 01:23 generated 50.00

grep your debug.log for "generated" to see what you've generated, and grep for "hashmeter" to see the performance. On windows, use:
findstr "hashmeter generated" "%appdata%\bitcoin\debug.log"

I have the hashmeter messages once an hour. How often do you think it should be?

theymos

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Thanks for clearing that up, fergalish!

fergalish

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Quote from: lachesis on June 05, 2010, 11:28:29 AM

I thought about that. I don't know if 0.5 is valid or not. I'll continue to take observations. I wonder if it writes to the debug log when it has success.

Use a value of 1, not 0.5. Suppose max=100 and target=10, then 10 out of every 100 hashes will be at or below the target, so your success rate will be 10% NOT 5%.

At the moment target/max ~= 1.5x10^-11 (target~=0x000000000f, which is 36 zeros, so you basically need to throw a dice with 2^36=69 billion sides, and wait until you get a 1), and you're doing 1 million x 86400 = 86.4 billion hashes per day, so you can expect slightly more than one success per day.

It's VERY important to realise that this is the AVERAGE bitcoin creation time, and will only be valid over periods longer than about a week or so. Because a success event is completely random (I hope, otherwise the hash function is probably not secure and someone will eventually crack it, and therefore bitcoin!), the interval between one success and the next will follow a Poisson distribution with n=0, i.e. an exponential (see wikipedia). Therefore, with an average rate of, say, 1 success per day, you can expect that roughly 10% of the time, you'll have to wait 2¼ days or more, 1% of the time 4½ days, 0.1% 7 days and so on.

theymos

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Quote

I wonder if it writes to the debug log when it has success.

BitCoin does say when it has solved a block. Search for "proof-of-work found".

Quote

In Bitcoin, aren't multiple nodes working on the same block?

No. Each node's block is unique because it contains their unique public key. Functionally, every hash gives you a totally random number between 0 and the maximum value of a 256-bit number. If the random number is equal to or below the target, you win. So the probability of winning with one hash is target in max.

Starting on another block because somebody else won requires almost no work.

See the BitCoin Wiki "block" article and the BitCoin paper for more info.

Topic: Proof-of-work difficulty increasing - page 2. (Read 37041 times)