Evaluation of gas usage when duplicates discovery implemented with simple arrays (O(n^2))

results.md

Array of different size was sent to hasEnoughValidSignatures() method in the set of experiments. As soon as the transactions was mined, the transaction receipt was get to extract gasUsed value.

num of elements	gas usage by tx
4	51885
6	58591
8	66561
10	75796
12	86230
14	97993
16	111019
18	125246
20	140801

test.sol

pragma solidity ^0.4.23;

contract Test {
    mapping (uint256 => uint256) public gasUsed;
    
    function addressArrayContains(address[] array, address value) internal pure returns (bool) {
        for (uint256 i = 0; i < array.length; i++) {
            if (array[i] == value) {
                return true;
            }
        }
        return false;
    }
    
    function hasEnoughValidSignatures(address[] _vs) public {
        address[] memory encounteredAddresses = new address[](_vs.length);

        //gasleft is used for nothing just to change something in the storage
        uint256 current = gasleft();
        for (uint8 i = 0; i < _vs.length; i++) {
            address recoveredAddress = _vs[i];
            if (addressArrayContains(encounteredAddresses, recoveredAddress)) {
                //in the test it never should be here
                gasUsed[_vs.length] = 2**256-1;
            }
            encounteredAddresses[i] = recoveredAddress;
        }
        gasUsed[_vs.length] = current - gasleft();
    }
}