<<  >> (p.148)
    Author Topic: Eligius: 0% Fee BTC, 105% PPS NMC, No registration, CPPSRB  (Read 1062553 times)
    This is a self-moderated topic. If you do not want to be moderated by the person who started this topic, create a new topic.
    un_ordinateur
    Full Member
    ***
    Offline Offline

    Activity: 157
    Merit: 100


    View Profile
    July 22, 2014, 09:35:10 PM
     #2941

    i've also noticed does the diff rate only go like 256 512 1024? so there is no middle ground? like 720?

    Difficulty is a power of 2.

    Difficulty indirectly represents the number of zeroes a the binary representation of a block hash must begin with to be considered a valid share.

    The formula is :
    Number of zeros necessary = 32 + log2(difficulty).

    So a diff1 share begins with: 0000 0000 0000 0000 0000 0000 0000 0000 XXXX XXXX....

    A diff2 share adds one 0: 0000 0000 0000 0000 0000 0000 0000 0000 0XXX XXXX....
    Since it cuts in half the number of valid shares, the "difficulty" of finding a valid share is doubled.

    A diff4 share adds another 0:  0000 0000 0000 0000 0000 0000 0000 0000 00XX XXXX....
    The number of valid share is again cut in half, so the amount of work necessary to finding a valid share, relative to a diff1 share, is 4 times.

    You can see, then, how and why the difficulty is constrained to powers of two. Furthermore, putting a non-power of two in the above formula would result in a non-integer amount of zeros necessary, which is impossible.
    That's wrong. Difficulty can be anything including fractional values. It's a power of two as a cheap optimisation/numerical convenience for the pool software run here.

    Indeed, the full Bitcoin network has difficulty of any arbitrary value, but I've never seen a pool (any pool! not just this one) that sent share of values not multiple of two.
Page 147
Viewing Page: 148