Gas Optimizations

[code423n4]

Gas Optimizations

• Variables like UNREVEALED_URI and BASE_URI, which can't be changed, can be marked as immutable to save gas when accessing them.
• The mapping(uint256 => mapping(address => mapping(uint256 => uint256))) public getCopiesOfArtGobbledByGobbler; mapping can be changed to simplify it. We know the gobbler id will be maximum 10000, so it can fit in a uint96. That means that instead of mapping a gobbler id to an address of an nft, we can group them together and create the new mapping(uint256 => mapping(uint256 => uint256))) public getCopiesOfArtGobbledByGobbler;, where the first uint256 is the gobbler id and the nft contract's address grouped ((gobblerId << 160) | nft).
• Calculate toWadUnsafe(MAX_MINTABLE) in the ArtGobblers contract pre deployment so it will save gas on deployment.

• Cache storage variables to reduce the number of SLOADs

  • Cache legendaryGobblerAuctionData.numSold, getGobblerData[id] in the ArtGobblers.mintLegendaryGobbler
  • Use the cached value in ArtGobblers.legendaryGobblerPrice instead of accessing numMintedFromGoo again (uint256 numMintedSinceStart = numMintedFromGoo - numMintedAtStart; => uint256 numMintedSinceStart = mintedFromGoo - numMintedAtStart;)
  • Cache getGobblerData[swapId].idx and getGobblerData[currentId].idx in the ArtGobblers.revealGobblers function. The optimized code:

    
    uint idx = getGobblerData[swapId].idx;
    uint64 swapIndex = idx == 0
    ? uint64(swapId) // Hasn't been shuffled before.
    : idx; // Shuffled before.

  // Get the owner of the current id. address currentIdOwner = getGobblerData[currentId].owner;

  // Get the index of the current id. idx = getGobblerData[currentId].idx; uint64 currentIndex = idx == 0 ? uint64(currentId) // Hasn't been shuffled before. : idx; // Shuffled before.

• Modify the expression legendaryGobblerAuctionData.startPrice = uint120(cost <= LEGENDARY_GOBBLER_INITIAL_START_PRICE / 2 ? LEGENDARY_GOBBLER_INITIAL_START_PRICE : cost * 2); in the ArtGobblers.mintLegendaryGobbler function by:
  1. Changing cost <= LEGENDARY_GOBBLER_INITIAL_START_PRICE / 2 to 2 * cost <= LEGENDARY_GOBBLER_INITIAL_START_PRICE
  2. Changing 2 * cost to cost << 1
  3. Cache the value of cost << 1 instead of calculating it twice The final expression:

     uint doubleCost = cost << 1;
     legendaryGobblerAuctionData.startPrice = uint120(doubleCost <= LEGENDARY_GOBBLER_INITIAL_START_PRICE ? LEGENDARY_GOBBLER_INITIAL_START_PRICE : doubleCost);

• Use shifting instead of multiplying by powers of 2 in the ArtGobblers.mintLegendaryGobbler function (getGobblerData[gobblerId].emissionMultiple = uint32(burnedMultipleTotal * 2) => getGobblerData[gobblerId].emissionMultiple = uint32(burnedMultipleTotal << 1))
• Use prefix incrementation and decrementation when incrementing or decrementing variables by one:
  • line 464 of the ArtGobblers.mintLegendaryGobbler function - legendaryGobblerAuctionData.numSold += 1 => ++legendaryGobblerAuctionData.numSold
  • line 906 - getUserData[from].gobblersOwned -= 1; => --getUserData[from].gobblersOwned;
  • line 913 - getUserData[to].gobblersOwned += 1; => ++getUserData[to].gobblersOwned;
• Create a constant for the last non-legendary gobbler id instead of calculating FIRST_LEGENDARY_GOBBLER_ID - 1 in every iteration of the loop in ArtGobblers.revealGobblers
• Use & (2 ** 64 - 1) instead of % 2 ** 64. (randomSeed := mod(keccak256(0, 32), shl(64, 1)) => randomSeed := and(keccak256(0, 32), 0xffffffffffffffff))
• Optimize this condition using the following steps:
  1. newNumMintedForReserves > (numMintedFromGoo + newNumMintedForReserves) / 5
  2. 5 * newNumMintedForReserves > numMintedFromGoo + newNumMintedForReserves
  3. 4 * newNumMintedForReserves > numMintedFromGoo
  4. (newNumMintedForReserves << 2) > numMintedFromGoo

[GalloDaSballo]

Variables like UNREVEALED_URI and BASE_URI, which can't be changed, can be marked as immutable to save gas when accessing them.

4.2k

getCopiesOfArtGobbledByGobbler

This saves the keccak cost, at the cost of packing, so prob 20 gas

400 gas from SLAODs

Modify the expression legendaryGobblerAuctionData.startPrice = uint120(cost <=

We know shift wont' save gas (sponsor feedback) 3 gas from caching the other value

Use prefix incrementation and decrementation when incrementing or decrementing variables by one:

Prefix is 11 per instance = 33

Neat unique report, would recommend using bigger blocks for code, but really nice jbo!

4636

[transmissions11]

Decided to selectively implement some of them. Lots of clever and good optimizations but not all are worth the readability costs.