Backd contest - NoamYakov's results

Unnecessary checked arithmetic in for loops

There is no risk of overflow caused by increments to the iteration index in for loops (the i++ in for (uint256 i = 0; i < numIterations; i++)). Increments perform overflow checks that are not necessary in this case.

Recommendation

Surround the increment expressions with an unchecked { ... } block to avoid the default overflow checks. For example, change the loop

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

to

for (uint256 i = 0; i < numIterations;) {
	// ...
	unchecked { i++; }
}

It is a little less readable but it saves a significant amount of gas.

Unnecessary SLOADs and MLOADs in for-each loops

There are many for loops that follows this for-each pattern:

for (uint256 i = 0; i < array.length; i++) {
	// do something with `array[i]`
}

In such for loops, the array.length is read on every iteration, instead of caching it once in a local variable and read it from there. Storage reads are much more expensive than reading local variables. Memory reads are a bit more expensive than reading local variables.

Recommendation

Read these values from storage / memory once, cache them in local variables and then read them again from the local variables. For example:

uint256 length = array.length;
for (uint256 i = 0; i < length; i++) {
	// do something with `array[i]`
}

Prefix increments / decrements are cheaper than postfix increments / decrements

Use prefix increments / decrements (++x / --x) instead of postfix increments / decrements (x++ / x--).

Recommendation

Change all postfix increments / decrements to prefix increments / decrements.