VTVL contest - subtle77's results

1 Using > 0 costs more gas than != 0 when used on a uint in a require() statement.Saves 6 gas

• contracts/token/VariableSupplyERC20Token.sol

27 require(initialSupply_ > 0 || maxSupply_ > 0, "INVALID_AMOUNT");

• contracts/token/FullPremintERC20Token.sol

11 require(supply_ > 0, "NO_ZERO_MINT");

• tvl/contracts/VTVLVesting.sol

107 require(_claim.startTimestamp > 0, "NO_ACTIVE_CLAIM");

256 require(_linearVestAmount + _cliffAmount > 0, "INVALID_VESTED_AMOUNT");

257 require(_startTimestamp > 0, "INVALID_START_TIMESTAMP");

263 require(_releaseIntervalSecs > 0, "INVALID_RELEASE_INTERVAL");

449 require(bal > 0, "INSUFFICIENT_BALANCE");

2 ++I COSTS LESS GAS COMPARED TO I++ OR I += 1 IN FOR LOOPS (~5 GAS PER ITERATION) ++i costs less gas compared to i++ or i += 1 for unsigned integer, as pre-increment is cheaper (about 5 gas per iteration). This statement is true even with the optimizer enabled.

i++ increments i and returns the initial value of i.++i returns the actual incremented value with i++ the compiler has to create a temporary variable (when used) for returning 1 instead of 2.

• contracts/VTVLVesting.sol

353 for (uint256 i = 0; i < length; i++)

3 Splitting require() statements that use && saves gas.Saves 8 gas per && Instead of using the && operator in a single require statement to check multiple conditions,using multiple require statements with 1 condition per require statement will save 8 GAS per && The gas difference would only be realized if the revert condition is realized(met).

• contracts/VTVLVesting.sol 344 require(_startTimestamps.length == length && 345 _endTimestamps.length == length && 346 _cliffReleaseTimestamps.length == length && 347 _releaseIntervalsSecs.length == length && 348 _linearVestAmounts.length == length && 349 _cliffAmounts.length == length, 350 "ARRAY_LENGTH_MISMATCH"

The above should be modified to

require( _startTimestamps.length == length,
            "ARRAY_LENGTH_MISMATCH");
  require(  _endTimestamps.length == length,
            "ARRAY_LENGTH_MISMATCH";
     require(  _cliffReleaseTimestamps.length == length,
            "ARRAY_LENGTH_MISMATCH");
    require( _releaseIntervalsSecs.length == length,
            "ARRAY_LENGTH_MISMATCH");
     require(  _linearVestAmounts.length == length,
            "ARRAY_LENGTH_MISMATCH");
       require( _cliffAmounts.length == length,
            "ARRAY_LENGTH_MISMATCH");

4 Cache storage values in memory to minimize SLOADs

The code can be optimized by minimising the number of SLOADs. SLOADs are expensive 100 gas compared to MLOADs/MSTOREs(3gas) Storage value should get cached in memory

• contracts/token/VariableSupplyERC20Token.sol

36function mint(address account, uint256 amount) public onlyAdmin { 37 require(account != address(0), "INVALID_ADDRESS"); 38 // If we're using maxSupply, we need to make sure we respect it 39 // mintableSupply = 0 means mint at will 40 if(mintableSupply > 0) { 41 require(amount <= mintableSupply, "INVALID_AMOUNT"); 42 // We need to reduce the amount only if we're using the limit, if not just leave it be 43 mintableSupply -= amount; 44 } 45 _mint(account, amount); 46 } Caching mintableSupply as a local variable