Explanation for small variation in gasUsed while recursively deploying same contract

Question

https://github.com/christianlundkvist/simple-multisig/blob/master/contracts/SimpleMultiSig.sol

I'm deploying the above contract recursively and I find that the gasUsed varies by specifically 12 gas. The array of owners stays the same length between deploys, however the addresses change. Could the change in addresses change effect the computation cost?

gasUsed: 1391022 gasUsed: 1391010

  constructor(uint threshold_, address[] owners_, uint chainId) public {
    require(owners_.length <= 10 && threshold_ <= owners_.length && threshold_ > 0);

    address lastAdd = address(0);
    for (uint i = 0; i < owners_.length; i++) {
      require(owners_[i] > lastAdd);
      isOwner[owners_[i]] = true;
      lastAdd = owners_[i];
    }
    ownersArr = owners_;
    threshold = threshold_;

    DOMAIN_SEPARATOR = keccak256(abi.encode(EIP712DOMAINTYPE_HASH,
                                            NAME_HASH,
                                            VERSION_HASH,
                                            chainId,
                                            this,
                                            SALT));
  }

Answer 1

You have to pay some gas for every byte in data field of a transaction.

After Istanbul fork new cost are given in EIP 2028

• 16 gas a non-zero byte (it was 68 gas)
• 4 gas a zero byte (it didn't change)

So if your addresses have a zero byte the transaction will be 12 gas cheaper.