Understanding difficulty

[Altoidnerd]

4/1 means it found a difficulty 4 share, but it only need a difficulty 1 share.  It counts as a difficulty 1 share still when you submit it.

Does the mining software determine the sharediff of an Accepted share, or does the pool respond?

How is the fraction x/y arrived at for a given submission?  Is it a measure of the leading zeros?

[1714100773]

1714100773

[1714100773]

1714100773

[1714100773]

1714100773

[konradp]

Thank you all.

[-ck]

Share diff is chosen by the pool to find an optimal spread between bandwidth to the pool and variance to the miner. The choice of value chosen by the pool is arbitrary but most target diff to work out to somewhere around 20 shares submitted by the miner per minute. Difficulty of the share submitted is paid only based on the share difficulty asked for by the pool, though it can be much much higher (and ideally higher than the network difficulty in order to solve a block for the pool). Difficulty is internally determined in cgminer by checking the ratio of the share hash to diff1 where diff 1 is 26959535291011309493156476344723991336010898738574164086137773096960. Imagine every share's hash is just one massive number.

The 65536 constant mentioned earlier has nothing to do with bitcoin. Ignore it.

[whaSasd]

If difficulty grows by 20% do my earnings tank by 20%? Any reputable site that predicts difficulty? There are a few but they estimate different values.

[-ck]

If difficulty grows by 20% do my earnings tank by 20%? Any reputable site that predicts difficulty? There are a few but they estimate different values.

Yes and no respectively.

[tacotime]

http://bitcoin.stackexchange.com/questions/2924/how-to-calculate-new-bits-value

is the explanation I like to give.

Bitcoin has difficulty 1 set as eight leading zeroes for a share (0x00000000FFFF0000000000000000000000000000000000000000000000000000 in expanded form).  Then you get the numerical difficulty we're familiar with if you divide this by the current target (nBits) in expanded form.

Difficulty and nBits (target) are interconvertible; note that pools often use 256-bit expanded form: 0x00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF being diff 1.

[-ck]

Difficulty and nBits (target) are interconvertible; note that pools often use 256-bit expanded form: 0x00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF being diff 1.

This was only true of the getwork mining era. All stratum pools (should) use true diff 1 as their base now.

[DeathAndTaxes]

65536 is the average number of hashes to be computed in order to find a 1 share at mining difficulty 1 for a bitcoin based coin.

Not sure where you got 65536 from but it isn't correct.  It takes 2^32 hashes on average to find one which meets the target for difficulty 1. 

[-ck]

65536 is the average number of hashes to be computed in order to find a 1 share at mining difficulty 1 for a bitcoin based coin.

Not sure where you got 65536 from but it isn't correct.  It takes 2^32 hashes on average to find one which meets the target for difficulty 1. 

Look at his name, that will give you the clue where the 65536 comes from. It's an scrypt mining quirk.