⛔Gas Saving Technique 11: > 0 is less efficient than != 0 for unsigned integers

Book an audit with Zokyo

Introduction

Efficiency in smart contracts is fundamental, especially concerning gas consumption on the Ethereum network. Minor tweaks and optimizations in the contract can lead to gas savings. One such subtle yet effective technique is using != 0 instead of > 0 for comparison checks with unsigned integers, particularly within require statements when the optimizer is enabled.

Impact & Details

Understanding Gas Consumption

• Gas Cost Variations: When using comparisons for unsigned integers, the choice of comparison operator can influence the gas cost. Specifically, != 0 is slightly more gas-efficient than > 0 within require statements under optimized conditions.

Gas Savings with != 0

• Optimizer Efficiency: With the optimizer enabled, using != 0 for comparisons in require statements saves about 6 gas per operation compared to using > 0.

How to Implement != 0 for Gas Savings

Practical Example: Efficient Comparison Operation

Below is an example demonstrating this optimization:

Before Optimization:

solidityCopy code// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract EfficientComparison {
    function validateAmount(uint256 amount) public pure {
        require(amount > 0, "Amount must be greater than zero");
    }
}

After Optimization:

solidityCopy code// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract EfficientComparison {
    function validateAmount(uint256 amount) public pure {
        require(amount != 0, "Amount cannot be zero");
    }
}

In the optimized version, the comparison check is changed from > 0 to != 0, leading to a small gas saving for every transaction invoking this check.

Recommended Mitigation Steps

1. Identify Comparison Checks: Scan through your smart contracts for comparison checks using > 0 within require statements.

2. Use != 0 for Checks: Update the identified checks, replacing > 0 with != 0 to achieve gas savings per operation.

3. Test: Thoroughly test to ensure that this minor change does not inadvertently affect the functionality of the contract while implementing gas savings.

Conclusion

While the gas saving per transaction might seem marginal, optimizing comparison checks by using != 0 over > 0 can accumulate into more substantial savings over multiple transactions. This optimization becomes especially relevant for smart contracts that anticipate high volumes of transactions, where even small savings per transaction result in significant aggregate savings. Ensure to perform meticulous testing after implementing such optimizations to confirm that the smart contract behaves as expected while being more gas-efficient.