Gas Optimizations

[code423n4]

> 0 is less efficient than != 0 for unsigned integers (with proof)

!= 0 costs less gas compared to > 0
for unsigned integers in require statements with the optimizer enabled (6 gas)

Proof: While it may seem that > 0 is cheaper than !=,
this is only true without the optimizer enabled and outside a require statement.
If you enable the optimizer at 10k AND you’re in a require statement,
this will save gas. You can see this tweet for more proofs:
https://twitter.com/gzeon/status/1485428085885640706
I suggest changing > 0 with != 0 here:

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L195
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L764

for loops can be more efficient

To optimize the for loop and make it consume less gas, i suggest to:

1. If a variable is not set/initialized, it is assumed to have the default value (0 for uint, false for bool, address(0) for address…). Explicitly initializing it with its default value is an anti-pattern and wastes gas.

2. Use ++i instead of i++, which is a cheaper operation (in this case there is no difference between i++ and ++i because we dont use the return value of this expression, which is the only difference between these two expression).

3. Reading array length at each iteration of the loop takes 6 gas (3 for mload and 3 to place memory_offset) in the stack.

Caching the array length in the stack saves around 3 gas per iteration. I suggest storing the array’s length in a variable before the for-loop.

As an example:

for (uint256 i = 0; i < numIterations.length; ++i) { 

should be replaced with

for (uint256 i; i < newVariable; ++i) {

I suggest to change the code here:

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L248
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L311
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L322
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L710
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L624
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Project.sol#L368

consider using require instead of &&

SPLITTING REQUIRE() STATEMENTS THAT USE && SAVES GAS
Instead of using the && operator in a single require statement to check multiple conditions, I suggest using multiple require statements with 1 condition per require statement (saving 3 gas per &):

https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L61
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Disputes.sol#L106
https://github.com/code-423n4/2022-08-rigor/blob/b17b2a11d04289f9e927c71703b42771dd7b86a4/contracts/Community.sol#L353