I've created a private test network. On the genesis.json file, I've changed the difficulty to 1. Yet, mining a block still takes hours on my CPU. I suspect that is due to some configuration related to the network adaptation.
What is the correct procedure to decrease the difficulty on a private testnet, so that I can mine the first blocks in a not very powerful CPU?
There are 2 ways to do this:
Change the value of difficulty parameter in genesis.json file to a small number(preferably set it to 0). You can refer to this example genesis file
{
"config": {
"chainId": 1994,
"homesteadBlock": 0,
"eip155Block": 0,
"eip158Block": 0,
"byzantiumBlock": 0
},
"difficulty": "0x0", //difficulty set to zero in hexadecimal format
"gasLimit": "0x8000000",
"alloc": {
"9a963d0eefeb62678d8efb48561c81e51c552797": {
"balance": "9606938044258990275541962092341162602522202993782792835301376"
},
"30f28686aef33adbfbc13797b1d9f5a2f2759f56": {
"balance": "9606938044258990275541962092341162602522202993782792835301376"
}
}
}
Problem with this method is that when the block number increases, the difficulty also starts increasing at a high rate. So, to tackle that problem refer to the below part.
consensus.go which resides at consensus/ethash/consensus.go and search for the below line. return CalcDifficulty(chain.Config(), time, parent)
Now replace the above line with the below one.
return big.NewInt(1).
Now build the go-ethereum using make geth command.
I strongly recommend you to go through this article for much detailed implementation of the above process.
You can make the difficulty static by modifying the CalcDifficulty in Geth to return a static number. Example:
func CalcDifficulty(config *ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
return big.NewInt(1)
}
Rebuild Geth and use your modified version.
Source: Answer to Is it possible to change the block target time?
enode that I am connecting into? If yes, does it affect the difficulty on ongoing private blockchain network (ex: already mined 491,312 number of blocks)? @ eth♦
As seen in this blog
difficulty A scalar value corresponding to the difficulty level applied during the nonce discovering of this block. It defines the mining Target, which can be calculated from the previous block’s difficulty level and the timestamp. The higher the difficulty, the statistically more calculations a Miner must perform to discover a valid block. This value is used to control the Block generation time of a Blockchain, keeping the Block generation frequency within a target range. On the test network, we keep this value low to avoid waiting during tests, since the discovery of a valid Block is required to execute a transaction on the Blockchain.
The difficulty is set to 0x4000 in the genesis block, which is helping me mine block in every ~5 seconds.
I0401 07:06:16.533385 4556 ethash.go:252] Generating DAG: 98%
I0401 07:06:16.533482 4556 ethash.go:252] Generating DAG: 99%
I0401 07:06:16.533586 4556 ethash.go:252] Generating DAG: 100%
I0401 07:06:16.533668 4556 ethash.go:237] Done generating DAG for epoch 0, it took 10.562412ms
And Mining
I0401 07:06:26.062135 4556 worker.go:348] 🔨 Mined block (#219 / 9704b2d0). Wait 5 blocks for confirmation
I0401 07:06:26.062687 4556 worker.go:569] commit new work on block 220 with 0 txs & 0 uncles. Took 484.843µs
I0401 07:06:26.063166 4556 worker.go:569] commit new work on block 220 with 0 txs & 0 uncles. Took 375.001µs
I0401 07:06:32.221697 4556 worker.go:348] 🔨 Mined block (#220 / 77bb4f70). Wait 5 blocks for confirmation
I0401 07:06:32.222280 4556 worker.go:569] commit new work on block 221 with 0 txs & 0 uncles. Took 521.439µs
You can follow this tutorial with detailed explanation: http://blog.coinfabrik.com/fast-smart-contracts-execution-ethereum-private-blockchain-development-environment/
