Gas Optimizations

[code423n4]

Splitting require() statements that use && saves gas - 8 gas per &&

Instead of using the && operator in a single require statement to check multiple conditions,using multiple require statements with 1 condition per require statement will save 8 GAS per && The gas difference would only be realized if the revert condition is realized(met).

File:InfinityExchange.sol line 264

    require(numSells == buys.length && numSells == constructs.length, 'mismatched lengths');

The above should be modified to

     require(numSells == buys.length,'mismatched lengths');
       require(numSells == constructs.length, 'mismatched lengths');

File: InfinityExchange.sol line 949

    require(makerOrderValid && executionValid, 'order not verified');

The above should be modified to

     require(makerOrderValid,'order not verified');
       require(executionValid, 'order not verified');

Proof The following tests were carried out in remix with both optimization turned on and off

    require ( a > 1 && a < 5, "Initialized");
    return  a + 2;
}

Execution cost 21617 with optimization and using && 21976 without optimization and using &&

After splitting the require statement

    require (a > 1 ,"Initialized");
    require (a < 5 , "Initialized");
    return a + 2;
}

Execution cost 21609 with optimization and split require 21968 without optimization and using split require

Comparisons: != is more efficient than > in require

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

For uints the minimum value would be 0 and never a negative value. Since it cannot be a negative value, then the check > 0 is essentially checking that the value is not equal to 0 therefore >0 can be replaced with !=0 which saves 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. see

I suggest changing > 0 with != 0 here:

File: InfinityExchange.sol line 392

    require(numNonces > 0, 'cannot be empty');

The above should be modifed to:

    require(numNonces != 0, 'cannot be empty');

Something similar to my proposal is already implemented here File: InfinityStaker.sol line 68

    require(amount != 0, 'stake amount cant be 0');

use shorter revert strings(less than 32 bytes)

You can (and should) attach error reason strings along with require statements to make it easier to understand why a contract call reverted. These strings, however, take space in the deployed bytecode. Every reason string takes at least 32 bytes so make sure your string fits in 32 bytes or it will become more expensive.

Shortening revert strings to fit in 32 bytes will decrease deployment time gas and will decrease runtime gas when the revert condition is met.

Revert strings that are longer than 32 bytes require at least one additional mstore, along with additional overhead for computing memory offset, etc.

File: InfinityExchange.sol line 395

      require(!isUserOrderNonceExecutedOrCancelled[msg.sender][orderNonces[i]], 'nonce already executed or cancelled');

File:InfinityStaker.sol line 92

    require(
      userstakedAmounts[msg.sender][oldDuration].amount >= amount,
      'insufficient staked amount to change duration'
    );

File:InfinityStaker.sol line 96

    require(newDuration > oldDuration, 'new duration must be greater than old duration');

I suggest shortening the revert strings to fit in 32 bytes, or using custom errors which is explained below

Use Custom Errors instead of Revert Strings to save Gas

Custom errors from Solidity 0.8.4 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met)

see Source

Starting from Solidity v0.8.4, there is a convenient and gas-efficient way to explain to users why an operation failed through the use of custom errors. Until now, you could already use strings to give more information about failures (e.g., revert("Insufficient funds.");), but they are rather expensive, especially when it comes to deploy cost, and it is difficult to use dynamic information in them.

Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).

Using unchecked blocks to save gas

Solidity version 0.8+ comes with implicit overflow and underflow checks on unsigned integers. When an overflow or an underflow isn’t possible (as an example, when a comparison is made before the arithmetic operation), some gas can be saved by using an unchecked block

File: InfinityExchange.sol line 1156

    uint256 priceDiff = startPrice > endPrice ? startPrice - endPrice : endPrice - startPrice;

Note: Before the subtraction operation is carried out, we have a check that is executed. The first arithemetic startPrice - endPrice will be executed if the condition startPrice > endPrice is true. This means startPrice must be greater than endPrice so no underflow would occur here. The second part of the subtraction arithemetic endPrice - startPrice would be executed only if the check startPrice > endPrice fails which would mean startPrice not greater than endPrice therefore the operation endPrice - startPrice would not underflow as endPrice is guaranted to be greater than startPrice

The above should be modified to

unchecked{
    uint256 priceDiff = startPrice > endPrice ? startPrice - endPrice : endPrice - startPrice;
    }

Other instances to modify

File: InfinityExchange.sol line 1164

    return startPrice > endPrice ? startPrice - priceDiff : startPrice + priceDiff;

File:InfinityOrderBookComplication.sol line 333

    uint256 priceDiff = startPrice > endPrice ? startPrice - endPrice : endPrice - startPrice;

FIle:InfinityStaker.sol line 301

      amount = amount - noVesting;

The above cannot underflow due to the check on line 298 that ensures that amount is greater than noVesting. see below

    if (amount > noVesting) {

FIle:InfinityStaker.sol lne 305

        amount = amount - vestedThreeMonths;

The above cannot underflow due the check on line 302

FIle:InfinityStaker.sol line 309

          amount = amount - vestedSixMonths;

The above cannot underflow due to the check on line 306

No need to initialize variables with their default values

If a variable is not set/initialized, it is assumed to have the default value (0, false, 0x0 etc depending on the data type). If you explicitly initialize it with its default value, you are just wasting gas. It costs more gas to initialize variables to zero/false than to let the default of zero/false be applied

File: InfinityOrderBookComplication.sol line 42

    bool _isPriceValid = false;

The default values for booleans is false therefore no need to initialize it here. so the above should be declared as follows

    bool _isPriceValid;

Something similar to my proposal was implemented a few lines after that but for uint256

File: InfinityOrderBookComplication.sol line 45

    uint256 execPrice;

Other Instances to modify File: InfinityOrderBookComplication.sol line 108

    bool _isPriceValid = false;

File: InfinityOrderBookComplication.sol line 214

    uint256 numTakerItems = 0;

File: InfinityOrderBookComplication.sol line 244 File: InfinityOrderBookComplication.sol line 289 File: InfinityOrderBookComplication.sol line 318

[nneverlander]

Thanks