Zokyo Gas Savings
  • โ›ฝZokyo Gas Savings
  • ๐Ÿ“šTutorials
    • โœ”๏ธGas Saving Technique 1: Unchecked Arithmetic
    • โ›“๏ธGas Saving Technique 2: Immutable Variable
    • โœจGas Saving Technique 3: Double star ** inefficiency
    • ๐Ÿ’ฐGas Saving Technique 4: Cache Array Length
    • โฌ…๏ธGas Saving Technique 5: ++i costs less gas compared to i++
    • โš–๏ธGas Saving Technique 6: NOT operator ! cheaper than boolean FALSE
    • ๐ŸชกGas Saving Technique 7: Using Short Reason Strings
    • ๐ŸชตGas Saving Technique 8: Use Custom Errors instead of Revert Strings to save Gas
    • โœ’๏ธGas Saving Technique 9: Use Custom Errors instead of Revert Strings to save Gas
    • ๐Ÿ‘พGas Saving Technique 10: Calldata cheaper than memory
    • โ›”Gas Saving Technique 11: > 0 is less efficient than != 0 for unsigned integers
    • โž—Gas Saving Technique 12: SafeMath no longer needed
    • ๐Ÿ˜ฎGas Saving Technique 13: variables default to 0
    • ๐ŸงฑGas Saving Technique 14: struct layout/ variable packing
    • ๐Ÿ“žGas Saving Technique 15: Cache External Call
    • โœ๏ธGas Saving Technique 16: Early Validation before external call
    • ๐Ÿ˜ŽGas Saving Technique 17: Donโ€™t cache value that is used once
    • ๐Ÿ˜งGas Saving Technique 18: Redundant code
    • โœ…Gas Saving Technique 19: Early Validation before external call
    • โ›๏ธGas Saving Technique 20: Storage vs Memory read optimizations
    • โœ’๏ธGas Saving Technique 21: Unneeded If statements
    • ๐ŸŒ—Gas Saving Technique 22: >= is cheaper than >
    • ๐ŸŽ’Gas Saving Technique 23: Public to private constants
    • โน๏ธGas Saving Technique 24: Make unchanged variables constant/immutable
    • โฑ๏ธGas Saving Techniques 25: Redundant Access Control Checks
    • โžก๏ธGas Saving Technique 26: Shift Right instead of Dividing by 2
    • ๐ŸชƒGas Saving Tutorial 27: Efficient Boolean Comparison
    • ๐ŸคGas Saving Technique 28: && operator uses more gas
    • ๐Ÿ‘“Gas Saving Technique 29: x = x + y is cheaper than x += y
    • ๐Ÿ‘‚Gas Saving Technique 30: Using 1 and 2 rather than 0 and 1 saves gas
    • โšฝGas Saving Technique 31: Optimize Storage by Avoiding Booleans
    • ๐Ÿ”™Gas Saving Technique 32: Optimal Use of Named Return Variables in Solidity
    • ๐Ÿ›ข๏ธGas Saving Technique 33: Making Functions Payable for Optimized Gas Costs
    • โœ๏ธGas Saving Technique 34: Optimizing Storage References in Smart Contracts
    • โ›ฐ๏ธGas Saving Technique 35: Usage of uints/ints smaller than 32 bytes (256 bits) incurs overhead
    • ๐ŸŒช๏ธGas Saving Technique 36: Inlining Single Use Internal Functions for Savings
    • โ˜„๏ธGas Saving Technique 37: Switching from Public to External Functions for Savings
    • ๐ŸŽ†Gas Saving Technique 38: Upgrading Solidity Compiler to Improve Gas Efficiency and Security
    • ๐Ÿ•ถ๏ธGas Saving Technique 39: Avoiding Duplicated Code for Gas Savings
    • ๐Ÿ˜„Gas Saving Technique 40: Removal of Unused Internal Functions for Gas Savings
    • ๐Ÿ–‹๏ธGas Saving Tutorial 41: In-lining Single Use Modifiers For Gas Saving
    • โ›๏ธGas Saving Technique 42: `require` vs`assert`
Powered by GitBook
On this page
  1. Tutorials

Gas Saving Tutorial 27: Efficient Boolean Comparison

PreviousGas Saving Technique 26: Shift Right instead of Dividing by 2NextGas Saving Technique 28: && operator uses more gas

Last updated 1 year ago

Introduction: In smart contract development, every bit of gas saved is crucial, especially for functions that get called frequently. One common micro-optimization that often goes unnoticed is how boolean values are compared. In this tutorial, we'll show you how to make your boolean comparisons more gas-efficient in Solidity.

Concept: Booleans inherently represent true or false. Comparing them directly to true or false is redundant and slightly gas inefficient. Rather than using if (booleanValue == true), you can simply use if (booleanValue). For false checks, instead of if (booleanValue == false), if (!booleanValue) can be used.

Benefits include:

  1. Gas Efficiency: Avoiding the direct comparison conserves some gas as fewer opcodes are executed in the EVM.

  2. Code Clarity: Directly using the boolean value usually results in more readable and concise code.

Example:

Given the code snippet in a governance system:

solidityCopy codefunction voteOnProposal(uint256 proposalId)
    external
    onlyRegisteredVoter
{
    require(
        hasVoted[msg.sender][proposalId] == false, //@audit gas: instead of comparing to a constant, just use "hasVoted[msg.sender][proposalId]"
        "Voter has already voted on this proposal!"
    );
    ...
}

The optimized boolean comparison would be:

solidityCopy codefunction voteOnProposal(uint256 proposalId)
    external
    onlyRegisteredVoter
{
    require(
        !hasVoted[msg.sender][proposalId], // Simply negate the boolean value for a false check
        "Voter has already voted on this proposal!"
    );
    ...
}

Recommendation:

  1. Examine your contracts for boolean comparisons using == true or == false.

  2. Replace these direct comparisons with the efficient boolean evaluations.

  3. Test to make sure the logic remains consistent and the behavior is as intended.

Conclusion:

Though the savings from boolean comparison optimizations might seem minute, they add up to provide a more gas-efficient and cleaner codebase. In projects with a multitude of such comparisons, the aggregated savings over numerous transactions can be significant. Always aim for efficient, clean code that accomplishes the same objective with fewer operations.

๐Ÿ“š
๐Ÿชƒ
Book an audit with Zokyo