Diffculty

[afarzin]

How often does difficulty go up? I can't find one place that explains this aspect well. I noticed it just shot up by 3M

[Kuber]

3M? Current difficulty is at 877226.7. Difficulty increases after a certain number of solved Blocks. The overall hashrate is related to the amount which it will be increased, i think. Its even possible that the difficulty drops if for instance the total hashrate decreases extremely. I don't know exactly, that is what i have heard so far.
Quick block solving -> higher increase
Slow block solving -> lower increase
Block solving stagnates -> decrease

No correctness guaranteed.

Source: bitcoinwatch.com

[Hook^]

How often does difficulty go up? I can't find one place that explains this aspect well. I noticed it just shot up by 3M

Difficulty grows in almost perfect lock-step with the growth in computing horsepower on the BitNet network.  Check out these graphs:

http://bitcoin.sipa.be/

Notice how the red line almost exactly follows the growth in TH/S.

Over the last year the growth has averaged 4% a day.

So this is what to expect the difficulty to grow at.

[Hook^]

How often does difficulty go up? I can't find one place that explains this aspect well. I noticed it just shot up by 3M

Difficulty grows in almost perfect lock-step with the growth in computing horsepower on the BitNet network.  Check out these graphs:

http://bitcoin.sipa.be/

Notice how the red line almost exactly follows the growth in TH/S.

Over the last year the growth has averaged 4% a day.

So this is what to expect the difficulty to grow at.

Sorry, BitCoin network.

[afarzin]

So what happens in the coming September? No one can solve anything?

[dgtlmrln]

According to http://bitminer.info/

The cost to mine a single BTC varies wildly per day. This has to do with the way the blocks are calculated. Some days the difficulty is higher than other days. Today's current difficulty is: 877226.66666667

From what I'm reading in this post though, this isn't true? Or perhaps this was true when bitcoin first came into existence?

[Auspician]

The difficulty will always be adjusted to match the computing power of the network.  The idea is that the difficulty allows six blocks to be solved each hour.  If the networks hashing power goes up, obviously more blocks will be solved than desired, so the difficulty increases.  If the networks hashing power goes down, obviously less blocks will be solved than desired, so the difficulty decreases.

Think about it like this: There is only 300 BTCs that are distributed each hour, in stacks of 50 BTCs.  This means that if there is a total combined network hashing power of 8,628,000 Mhash/s and your hashing power is 500 Mhash/s, you have a 1/2876 chance of solving a block in any given hour, or a 1/17256 chance of solving any particular block before someone else.  (500/8628000 = 17256, 6 chances in an hour = 2876)

If the networks hashing power goes up, the difficulty must be increased as well so that no more and no less than an average of 6 blocks are completed in an hour.

[Hook^]

According to http://bitminer.info/

The cost to mine a single BTC varies wildly per day. This has to do with the way the blocks are calculated. Some days the difficulty is higher than other days. Today's current difficulty is: 877226.66666667

From what I'm reading in this post though, this isn't true? Or perhaps this was true when bitcoin first came into existence?

yes, per day.  But on average it grows about 4% a day because that is the growth of computing horsepower thrown at the problem.

[dgtlmrln]

I think I understand now...

As we get close to the year 2140 / 21,000,000 BTC, won't the difficulty drop? (all the more difficult blocks will have been solved and the 6 blocks / hour would be enforceable?)

[Hook^]

I think I understand now...

As we get close to the year 2140 / 21,000,000 BTC, won't the difficulty drop? (all the more difficult blocks will have been solved and the 6 blocks / hour would be enforceable?)

The only reason that later blocks are harder than earlier blocks is because more people have thrown computers at the problem, and the network has adjusted the difficulty so that the same bitcoins/day are produced.

If only 100 computers were on the network from beginning to end, the difficulty for every block would be the same from now until 2140.

[luxgladius]

Seems like there are some misunderstandings here. The difficulty is adjusted every 2016 blocks, which is about 2 weeks in real time. (Less if the network hashrate is growing during the interval.) It does not vary from one day to the next, unless one of the second day is a retargeting event. It will also not change the way that it works in 2040 or anything. Rather, the subsidy will continually increase every 210000 blocks (about 4 years) by a factor of 2. This is what leads to the final value approaching somewhat less than 21 million.

[SomeoneWeird]

Seems like there are some misunderstandings here. The difficulty is adjusted every 2016 blocks, which is about 2 weeks in real time. (Less if the network hashrate is growing during the interval.) It does not vary from one day to the next, unless one of the second day is a retargeting event. It will also not change the way that it works in 2040 or anything. Rather, the subsidy will continually increase every 210000 blocks (about 4 years) by a factor of 2. This is what leads to the final value approaching somewhat less than 21 million.

+1