Gas Optimizations

[code423n4]

Summary

Id	Title
1	Caching returned values from function calls can save gas
2	Cache length in the for loop and uncheck index

1. Caching returned values from function calls can save gas

External call to other contract is gas consuming and should avoid as much as possible.

For example, in Community.lendToProject() function, lenderFee() of _projectInstance is called 2 times. We should call only 1 time and cache the returned values to save gas.

Affected Codes

• https://github.com/code-423n4/2022-08-rigor/blob/5ab7ea84a1516cb726421ef690af5bc41029f88f/contracts/Community.sol#L393-L394

2. Cache length in the for loop and uncheck index

At each iteration of the loop, length is read from storage. We can cache the length and save gas per iteration.

Solidity 0.8.0 check safe math in every operation. Use uncheck to increase index can save gas.

For example

uint256 length = arr.length;
for (uint i; i < length; ) {
    // do stuff
    unchecked { ++i; }
}

Occurences

• https://github.com/code-423n4/2022-08-rigor/blob/5ab7ea84a1516cb726421ef690af5bc41029f88f/contracts/Project.sol#L603
• https://github.com/code-423n4/2022-08-rigor/blob/5ab7ea84a1516cb726421ef690af5bc41029f88f/contracts/Project.sol#L650