Bitcoin Forum

Someone was trying to explain this to me, but I still don't think I get it.  What exactly does the "best share" field on cgminer mean?  When I start mining it's in the hundreds and it sits there, but some days I cam back from work or sleeping and it shows all of a sudden anywhere from 3k to 30k.

I could not find anything in the readme that did a good job at explaining it.  Anyone wanna take a stab at it?

Mining works by hashing a bunch of transaction information over and over (millions of hashes per second), slightly changing a few pre-determined variables each time to get a brand new hash, and then comparing all of the resulting hashes to see if one of them fits a certain set of criteria, called the difficulty. When a hash succeeds in this, the resulting hash will have a difficulty of 1 (or higher), and is now considered a "share", as we can submit this share to a pool.

Shares can vary in their difficulty. It's sort of like drawing straws (http://en.wikipedia.org/wiki/Drawing_straws) with a bunch of different length straws: you never know how short the straw you're going to draw next is. The shorter the straw, the higher the difficulty, in our analogy. A share can have a difficulty of 1, 2 (twice has hard to find), 10 (10x harder), or 8,385,298 (8,385,298x harder to find). I don't know of any limit to how high the difficulty can go, but it gets incredibly harder to find higher difficulty shares.

A block is found when a share's difficulty is higher than the network difficulty. At the time of this writing, that's about 19.3million. All of those diff=1 shares you submit to your pool don't actually count for anything, except to prove to the pool that you're actually working on finding a block (share with diff>19.3M) for the pool.

Your "Best Share" is just a number to see how close you've come to finding a block. It's all completely random, so you could come back and find your GPU solved a block, or you could come back in a month and see you've never found anything higher. It's more of a fun, interesting number that doesn't really mean anything.

My 7970 in my desktop has a best share of 19.5K. If that were back in Jan of 2011 (https://docs.google.com/spreadsheet/ccc?key=0AmcTCtjBoRWUdHVRMHpqWUJValI1RlZiaEtCT1RrQmc#gid=0), that would have been higher than the Network Difficulty, and it would have been a block solver. Now, it's nowhere close.

Hope this helped answer your question.

Just wanted to say thanks for explaining the best share info in CGMiner. I know this is an old post, but I couldn't find anything else on Google that was as helpful :). By the way, best share over here is 14.9M, 12.7M etc after a couple days of mining. Boy does difficulty change.  :'(

old post but great explanation

Quite agree, couldn't work it out until I came across this. But today the difficulty is 2.19G? That's massive... Never never ever solve a block at this rate!

and that's why we have pools  ;)

I know it's a little silly, and makes no difference, but was nice to see a best share of 50.1m!