I would like to know if bitcoin pools can give a different difficulty value other than the network difficulty or is the network difficulty the same for everybody

  • at any given time if overall difficulty is at a certain number do pools respect that same difficulty number or can they go below the expected difficulty? – user14248 Mar 26 '14 at 22:16
  • I have reworded my question, I do hope for some feed back – user14248 Mar 27 '14 at 11:20

First of all, please be careful with using the terminology "network difficulty." Network difficulty is the difficulty at which a hash is accepted by the network (as opposed to the pool). Technically speaking, if d is the network difficulty, then your probability of finding a valid hash is 1/(d*2^32). If your question is interpreted literally, then the answer is trivially yes, since no pool would do such a thing. If everyone submits shares at the network difficulty, then the only share submitted is the one that solves the block, which means that the block finder gets the entire block reward, negating the reason people use pools (to reduce variance).

I guessing you're actually asking the following: Can mining pools give everyone a different difficulty?

The answer is yes. Basically, I might be mining at a difficulty of 16, and you could be mining at a difficulty of 32. If we have the same hashrate, then I would be finding shares twice as often as you, but your shares are worth twice as much. In the end, it all evens out. Mining at a lower difficulty reduces variance, but for miners with a large hashrate, their variance is already low enough that they can afford to mine at a higher difficulty, and they generally do so to reduce the stratum load (since they must communicate with the pool every time they submit a share).

There are several ways a pool could implement different difficulties. One is to have a setting on the pool website that you can adjust on your workers page. Another is to have multiple strata, each with a different difficulty. Yet another (which could be used in combination with the previous technique) is called vardiff, where the pool adjusts the difficulty to an optimal level in response to its estimate of your hashrate. Note that adjustment of share difficulty must be done at the pool level; there is no way to tell cgminer to choose a certain difficulty. (Even if you could, trying to submit a share at a difficulty lower than the pool wants will end up getting rejected, and only submitting those shares at a difficulty higher than the pool specifies will not get any bonus points for the extra difficulty.)

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