Arbitrum Nitro Gas Model

Gas Model Documentation
Project: Local testing patch for Arbitrum precompiles

Overview

This document describes the gas model implementation for the ArbGasInfo precompile handler in the Hardhat Arbitrum Patch plugin. The gas model approximates Nitro's baseline gas calculations for local development and testing.

Gas Model Components

1. L2 Base Fee

Default: 1 gwei (1,000,000,000 wei)
Purpose: Base cost for L2 transaction execution
Configurable: Via plugin configuration or gas config file

2. L1 Calldata Cost

Default: 16 gas per byte
Purpose: Cost for data posted to L1 (calldata compression)
Algorithm: calldataSize * l1CalldataCost * l1BaseFee

3. L1 Storage Cost

Default: 0 gas (Nitro has no storage gas concept)
Purpose: Reserved for future use or custom implementations
Note: Always 0 in current Nitro implementation

4. Congestion Fee

Default: 0 gas (no congestion fee by default)
Purpose: Dynamic fee adjustment based on network congestion
Configurable: Via plugin configuration

5. L1 Base Fee

Default: 20 gwei (20,000,000,000 wei)
Purpose: Base fee for L1 gas price estimation
Source: Configurable or read from mock oracle

Gas Calculation Algorithms

getCurrentTxL1GasFees()

TYPESCRIPT

function calculateL1GasFees(calldata: Uint8Array, l1BaseFee: bigint): bigint {
  const calldataSize = calldata.length;
  const l1GasUsed = calldataSize * 16; // 16 gas per byte
  return l1GasUsed * l1BaseFee;
}

getPricesInWei()

Returns 5-tuple: (l2BaseFee, l1CalldataCost, l1StorageCost, baseL2GasPrice, congestionFee)

getPricesInArbGas()

Returns 3-tuple: (l2BaseFee, l1CalldataCost, l1StorageCost) in ArbGas units

Configuration Options

Plugin Configuration

TYPESCRIPT

const config = {
  l1BaseFee: BigInt(20e9), // 20 gwei
  gasPriceComponents: {
    l2BaseFee: BigInt(1e9), // 1 gwei
    l1CalldataCost: BigInt(16), // 16 gas per byte
    l1StorageCost: BigInt(0), // No storage gas
    congestionFee: BigInt(0), // No congestion fee
  },
};

Gas Config File

JSON

{
  "l1BaseFee": "20000000000",
  "gasPriceComponents": {
    "l2BaseFee": "1000000000",
    "l1CalldataCost": "16",
    "l1StorageCost": "0",
    "congestionFee": "0"
  }
}