Asymmetry contest - 0xpanicError's results

https://github.com/code-423n4/2023-03-asymmetry/blob/main/contracts/SafEth/SafEth.sol

Gas Optimizations

[GAS-1] Intialise non-zero variables at the time of declaration

If a variable will hold a non-zero value then it should be set to a non-zero value at time of declaration.

preDepositPrice is declared and later set to either 10 ** 18 or (10 ** 18 * underlyingValue) / totalSupply. Instead it can be set to 10**18 and if total supply is not zero, set to (10 ** 18 * underlyingValue) / totalSuppl.

SSTORE requires 20000 gas from zero to non-zero but only 2900 from non-zero to non-zero

Instances (1):

File: contracts/SafEth/SafEth.sol

78:   uint256 preDepositPrice; // Price of safETH in regards to ETH

79:   if (totalSupply == 0)

80:      preDepositPrice = 10 ** 18; // initializes with a price of 1

81:   else preDepositPrice = (10 ** 18 * underlyingValue) / totalSupply;

[GAS-2] Cache array length in memory when called in loops

Whenever looping through an array, cache the array length in memory to save gas.

In the given loops, derivativesCount is called from storage for each iteration. Instead set derivativesCount in memory and call that in loops to save gas inside each function.

SLOAD requires 100 gas while MLOAD only requires 3 gas

Instances (5):

File: contracts/SafEth/SafEth.sol

71:   for (uint i = 0; i < derivativeCount; i++)

84:   for (uint i = 0; i < derivativeCount; i++)

113:  for (uint256 i = 0; i < derivativeCount; i++)

140:  for (uint i = 0; i < derivativeCount; i++)

147:  for (uint i = 0; i < derivativeCount; i++)

[GAS-3] If value is read only once, load directly from storage

If a storage variable is only read once, it's cheaper to read directly rather than storing it in memory.

totalSupply() is called only once but it's value is stored in memory and then read in the if statement. Instead the statement can directly read from storage if(!totalSupply()) and not call MSTORE and MLOAD.

Additional MSTORE and MLOAD take 6 gas

Instances (2):

File: contracts/SafEth/SafEth.sol

77:   uint256 totalSupply = totalSupply();

79:   if (totalSupply == 0)

File: contracts/SafEth/SafEth.sol

110:   uint256 safEthTotalSupply = totalSupply();

116:   _safEthAmount) / safEthTotalSupply;

[GAS-4] No need to loop to add or adjust totalWeight

totalWeight can directly be changed whenever a weights are adjusted or added. In the adjustWeight function, totalWeight could be set to totalWeight + _weight - weights[_derivativeIndex] before setting the mapping to the new value.

Similarly in addDerivative function, totalWeight could be set to totalWeight + _weight.

• Prevents unneccesary operations and saves gas

Instances (2):

File: contracts/SafEth/SafEth.sol

170:   uint256 localTotalWeight = 0;

171:   for (uint256 i = 0; i < derivativeCount; i++)

172:   localTotalWeight += weights[i];

173:   totalWeight = localTotalWeight;

File: contracts/SafEth/SafEth.sol

190:   uint256 localTotalWeight = 0;

191:   for (uint256 i = 0; i < derivativeCount; i++)

192:   localTotalWeight += weights[i];

193:   totalWeight = localTotalWeight;