7 Simple Ways to Optimize Gas in Solidity Smart Contracts

When deploying Ethereum smart contracts written in Solidity, transactions costs paid in gas can add up quickly. Finding ways to optimize gas usage is crucial for keeping fees lower. In this post we’ll explore 7 straightforward gas optimization techniques for Solidity developers.

1. Avoid Unnecessary Use of Storage

Writing data to storage is one of the most expensive operations in Solidity. Reduce gas costs by avoiding unnecessary writes. For example, move constant values to memory:

// Expensive
string public constant NAME = "MyContract"; 

// Cheaper
string memory NAME = "MyContract";

Also be careful about storing large pieces of data on-chain. Use alternative patterns like IPFS for larger data.

• Storing data costs 20,000 gas versus 3 gas for memory.
• Minimize storage by using memory for fixed constants and temporary values.
• Store large data like files off-chain (IPFS) and put hash on-chain.

2. Enable the ABI Encoder v2

The ABI encoder translates data types into the format stored on the blockchain. Enabling the newer v2 encoder saves gas:

pragma solidity ^0.8.0;

// Enable ABI encoder v2
pragma abicoder v2;

contract MyContract {
  //...
}

• Newer encoder uses less gas for structs, arrays, function params.
• But may break older clients – test compatibility.

3. Avoid Loops and Complex Computations

Loops that iterate or compute over arrays and mappings are expensive:

// Very expensive loop!
for (uint i = 0; i < users.length; i++) {
  // ...
}

Avoid loops when possible. If needed, limit iterations and computations inside them.

• Every iteration costs gas, so minimize loops.
• If needed, limit range and computations per loop.
• Map/filter/reduce patterns often cheaper than for loops.

4. Optimize Order of Expensive Ops

Some operations like SSTOREs are more expensive than SLOADs. Reorder statements to shift cheaper ops first:

mapping(address => uint) public balances;

function deposit() public payable {
  // SSTORE then SLOAD
  uint balance = balances[msg.sender]; 
  balance += msg.value;
  balances[msg.sender] = balance;
  
  // SLOAD then SSTORE (cheaper)
  uint balance = balances[msg.sender];
  balances[msg.sender] = balance + msg.value;
}

• Do cheaper SLOADs before more expensive SSTOREs.
• Move static calls like address(this) out of loops.
• Be aware of the gas cost order – SLOAD < other ops < SSTORE.

5. Precompute Off-Chain When Possible

Computing values in advance outside the blockchain is cheaper than doing it inside smart contracts:

// On-chain computation
function verify(uint numA, uint numB) {
  require(numA * numB < 1000);
}

// Precomputed off-chain
function verify(uint result) {
  require(result < 1000); 
}

• Do computations like hashes, signatures outside.
• Pass in precomputed values to save on-chain gas.
• Allows using faster languages like Python or Go.

6. Optimize Data Layout

Storing data contiguously in structs and arrays is cheaper than separate variables. Packed data costs less gas.

• Packed slots and contiguous storage is cheaper.
• Group commonly accessed data together.
• Order by size with smallest types first.

7. Use Events over Logs

For debugging, events are a cheaper way to record data than logs:

// More expensive
log("Deposit made");

// Cheaper 
event Deposit(address indexed user, uint amount);
emit Deposit(msg.sender, msg.value);

• Events are 75% cheaper for logging data.
• Useful for tracing and debugging.
• Indexed params help filter event logs.

Conclusion

Following gas optimization best practices will allow you to deploy leaner and more efficient smart contracts! Let me know if you need any clarification or have additional questions.

Posted in Blockchain, Ethereum, Smart ContractTagged blockchain, smart contracts, Solidity

By infuy

Infuy is an international technology leader company specialized in outsourcing services in the latest technologies. Blockchain (smart contracts, dApps and NFT marketplaces), full-stack, mobile development, and team augmentation are some of the areas where Infuy specializes in. As a software development company based in Uruguay with offices in the US, Infuy is always looking for the next big challenge, and the next big partner. As a fast-growing company, Infuy is always looking for talented and proactive people, who live up to the challenge and are as passionate as their team is about their mission to provide the best solutions to their partners, with the latest technologies, to join the team. For more information about the company and its services, please visit https://www.infuy.com/.