Talk:Block

2011-05-14T10:28:26Z

Henrythefifth:

== Each block contains all recent transactions, a nonce (random number), and the hash of the previous block. ==
The nonce is a seed that starts at zero and is incremented until the block hashes below the target.
Hence, it should not be called "random".

== What if I'm 1% towards calculating a block and...? ==

"There's no such thing as being 1% towards solving a block. You don't make progress towards solving it."

Is this true? I don't know if there's a nonce which will solve any given block, but for a block that is solvable, it's possible to be 1% of the way towards finding it. Supposing it takes 10 million attempts to 'solve' a block, then after 100,000 attempts you could say you were 1% towards solving it. You're certainly closer to solving it than you were before those 100,000 failed attempts, aren't you? [[User:Dooglus|Dooglus]] 05:05, 15 January 2011 (GMT)
:No one can know how many tries it will take to solve the block. After the fact you might say that at some point you had finished 1% of the necessary calculation for that block, but this was not really "progress".

:If you go back in time after completing a block and don't generate for one of the days that you did originally, then you could actually end up getting the block ''sooner'', as the work required is random. [[User:Theymos|theymos]] 11:06, 15 January 2011 (GMT)

Probabilistically speaking, one can make a "best guess" for how long it will take to solve a block. A problem with probabilistic estimation, for example, is that it may say it will take 10 hours to solve the block, with a standard deviation of 15 hours. How much more work do you have when you've worked on it for 10 hours? The answer is that you have ~10 hours more work :).

But assuming all incorrect hashes are exhausted first, the maximal number of tries needed to solve the block is ~2<sup>256</sup>. So, there exists an upper limit (albeit, it is an obscenely large one!) on the amount of work you can do. Progress is made, just very slowly. --[[User:Dlo|Dlo]] 20:28, 11 April 2011 (GMT)
:That's not the maximum. You can't predict the hash outcome, so you could try forever and still get values above the target. You'd get repeat hash values from the same input. [[User:Theymos|theymos]] 03:47, 18 April 2011 (GMT)
::I can predict the hash outcome by calculating SHA-256 with my mighty x86 processor. :) IMO "predicting" is irrelevant here. Dlo is assuming that the hash function is injective, therefore the number of incomes (giving outcome above the target) <= 2^256. But the hash function is not injective (by the cardinality argument: the set of incomes is infinite and the set of outcomes is finite). --[[User:Shrewdwatson|Shrewdwatson]] 13:49, 23 April 2011 (GMT)

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Talk:Block