Gas optimizations list

[G-01] Using == for uints to check for 0 value saves gas

Using == 0 when comparing uints instead of, for example, <= 0 is more gas efficient.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DecentralizedStableCoin.sol#L48

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DecentralizedStableCoin.sol#L61

[G-02] Use assembly to check for address(0)

Assembly can be used to more efficiently check for a zero address.

References:

• https://medium.com/@kalexotsu/solidity-assembly-checking-if-an-address-is-0-efficiently-d2bfe071331

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DecentralizedStableCoin.sol#L58

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L103

[G-03] Cache array length outside of for loop

Storing the array length before looping is more efficient as it prevents its length from being checked with each iteration.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L118

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L353

[G-04] Reduce gas usage by moving to Solidity 0.8.19 or later

See "References" below.

References

• https://blog.soliditylang.org/2023/02/22/solidity-0.8.19-release-announcement/#preventing-dead-code-in-runtime-bytecode

There are 3 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DecentralizedStableCoin.sol#L24

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L24

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/libraries\OracleLib.sol#L3

[G-05] Use unchecked{} for increments/decrements that cannot overflow

Use unchecked{i++} to avoid checking for underflows/overflows when appropriate, such as in a for loop, to save gas.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L118

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L353

[G-06] ++i costs less gas than i++, especially when it's used in for-loops (--i/i-- too)

This saves 5 gas per loop.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L118

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L353

[G-07] <x> += <y> costs more gas than <x> = <x> + <y> for state variables

Using the addition operator instead of plus-equals saves 113 gas per instance.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L155

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L198

[G-08] Re-initialising variables to their default value wastes gas

Setting for example a uint to 0 incurs overhead as 0 is already the default value when the variable is defined - there is no need to reset it to 0 again.

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L118

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L353

[G-09] Use constants instead of type(uintx).max

Using type(uintx).max such as type(uint128).max incurs more gas in distribution and for each transaction. Constants (such as 340282366920938463463374607431768211455 for type(uint128).max) should be used instead.

There is 1 instance of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L329

[G-10] Use hardcode address instead of address(this)

Instead of address(this), it is more gas-efficient to pre-calculate and use the address with a hardcode. Foundry's script.sol and solmate LibRlp.sol contracts can do this.

References:

• https://book.getfoundry.sh/reference/forge-std/compute-create-address

• https://twitter.com/transmissions11/status/1518507047943245824

There are 2 instances of this issue:

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L157

https://github.com/Cyfrin/2023-07-foundry-defi-stablecoin/blob/main/src/DSCEngine.sol#L274