CCIP gas estimator using Hardhat

This guide is designed to help you accurately estimate the gas consumption of the ccipReceive function within a CCIP Receiver contract. Understanding the gas dynamics of this function is crucial for setting an appropriate gasLimit when sending a CCIP message from the Sender contract.

The ccipReceive function is crafted for educational purposes to demonstrate how gas consumption changes with computational complexity. It is structured to accept a uint256 input representing the number of iterations a loop within the function will execute. This input is decoded from the received CCIP message as follows:

uint256 iterations = abi.decode(any2EvmMessage.data, (uint256)); // abi-decoding of the receiver number of iterations

To mitigate excessive gas consumption and ensure predictability, the iterations variable is internally capped at 99. The function achieves this by performing the modulo operation iterations % 100, thereby limiting the maximum number of iterations to 99. The core logic of the function, including the iteration cap and the loop, is outlined below:

// Initialize the result with the number of iterations
uint256 result = iterations;
// Cap the number of iterations to a maximum of 99
uint256 maxIterations = iterations % 100;

// Execute the loop, simulating computational work
for (uint256 i = 0; i < maxIterations; i++) {
    result += i;
}

By experimenting with different iterations values, developers can gain insights into optimal gas limit settings.

Local testing

1. Build the project.

forge build

1. Test and display the console.log instructions.

forge test -vv --isolate

Example output:

$ forge test -vv --isolate
[⠊] Compiling...
No files changed, compilation skipped

Ran 3 tests for test/SendReceive.t.sol:SenderReceiverTest
[PASS] test_SendReceiveAverage() (gas: 125166)
Logs:
  Number of iterations 50 - Gas used: 14740

[PASS] test_SendReceiveMax() (gas: 134501)
Logs:
  Number of iterations 99 - Gas used: 24099

[PASS] test_SendReceiveMin() (gas: 115581)
Logs:
  Number of iterations 0 - Gas used: 5190

Suite result: ok. 3 passed; 0 failed; 0 skipped; finished in 2.73ms (1.35ms CPU time)

Ran 1 test suite in 177.46ms (2.73ms CPU time): 3 tests passed, 0 failed, 0 skipped (3 total tests)

This table summarized the gas usage for different iterations:

Number of iterations	Gas used
0	5190
50	14740
99	24099

As you can notice from the output, the gas usage increases with the number of iterations. This is a crucial insight for setting the gasLimit when sending a CCIP message from the Sender contract. The maximum gas usage is observed when the number of iterations is set to 99 (gas: 24099).

Remark: Compare this with the results from the Hardhat guide.