Quote from: bitless on July 10, 2011, 05:16:27 PM

Thanks, Joel!

So, my understanding is that if we change any of these
1 then we have to rehash all previous parts of the message (i.e. the block), thus changing the first three words in the share on which a miner is working, and

That's correct. Changing the timestamp or coinbase gives you a whole universe of new nonces to try.

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2 this is what a pool does when all valid values of the nonce have been tried.

Most pools, to my knowledge, use the bitcoind client's logic to generate work units. With the fix from Luke Dash Jr., the logic looks like this:

void IncrementExtraNonce(CBlock* pblock, CBlockIndex* pindexPrev, unsigned int& nExtraNonce, int64& nPrevTime)
{ // Fix from Luke Dash Jr
static uint256 hashPrevBlock;
if (hashPrevBlock != pblock->hashPrevBlock)
{
nExtraNonce = 0;
hashPrevBlock = pblock->hashPrevBlock;
}
++nExtraNonce;
pblock->vtx[0].vin[0].scriptSig = CScript() << pblock->nBits << CBigNum(nExtraNonce);
pblock->hashMerkleRoot = pblock->BuildMerkleTree();
}

So the extra nonce (coinbase) goes to zero with each new block found on the network. Then increments in each work unit given to a client.

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Correct? Is there anything other than w[3] (that all kernels are currently changing) that we can change on the client side without having to change w[0] through w[2]?

I'm not 100% sure I understand what you're asking. Are you trying to be able to have miners generate their own new work units without having to go back to the pool? If so, it's a bit tricky because if they succeed in mining a block, you have to be able to assemble the correct block or you can't get paid.

If you're trying to have something other than the bitcoind program generate the work units (maybe you're trying to minimize the interactions between the pool manager and bitcoind) you're better off with the patches to speed it up. But in that case, you're best off replicating this same logic of increment the coinbase for each work unit, IMO.

You can't ever run out of things to try because by the time you ran through every combination of nonce and coinbase, the time would have changed. If you really want to, you can also change the payout address(es) in the coinbase transaction or drop/add a transaction.

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(Joel - I'll send you a whole 1 BTC when you answer this, even if the answer is a no

thank you very much!)

Thanks. I appreciate it. If I misunderstood your question, let me know.