Gas Mechanism

Overview

MAP Protocol v2 accurately estimates gas fees for each chain to ensure cross-chain transactions execute successfully without overcharging users. This document covers gas calculation, caching, oracles, and fee update mechanisms.

EVM Chain Gas Calculation

Gas Data Collection

Maintainer nodes obtain gas data by monitoring blocks, extracting the base fee and priority fees from block transactions.

Priority Fee Calculation

The system calculates a reasonable priority fee using the 25th percentile of priority fees from block transactions. This approach avoids outliers while ensuring transactions get included. The final gas price combines the base fee with the selected priority fee, with a minimum threshold applied.

Gas Cache Mechanism

To smooth gas price fluctuations, the system maintains a rolling cache of recent gas prices. The cache size is configurable via the gas_cache_blocks parameter, keeping only the most recent entries.

Transaction Gas Calculation

When sending transactions, the system uses statistical analysis:

1. Calculate the mean of cached gas prices

2. Calculate the standard deviation

3. Set gas fee cap = mean + 3 × standard deviation

4. Calculate tip cap as a percentage of fee cap

Parameter	Description
gas_price_resolution	Minimum gas price per chain
gas_cache_blocks	Number of blocks for gas cache
max_gas_tip_percentage	Maximum tip percentage

Bitcoin Chain Fee Calculation

Fee Data Retrieval

The system retrieves network fee information including minimum relay fee and block average fee rate from Bitcoin RPC calls.

Fee Rate Calculation

The fee rate is calculated to ensure the estimated transaction fee meets the network minimum relay fee requirement. If the initial estimate falls short, the rate is adjusted upward. A minimum sats-per-vbyte threshold is also enforced.

Transaction Size Estimation

Bitcoin transaction sizes are estimated based on:

Component	Size
Base overhead	~10 bytes
Per input (P2WPKH)	~68 bytes
Per output (P2WPKH)	~31 bytes

The system estimates sizes before UTXO selection to predict fees accurately.

Gas Oracle

Oracle Architecture

┌─────────────────────────────────────────────────────────────┐
│                     Gas Oracle System                        │
└─────────────────────────────────────────────────────────────┘

  Maintainer Nodes              MAP Relay Chain
       │                              │
       ▼                              ▼
┌─────────────┐               ┌─────────────┐
│  Observe    │──────────────▶│   GasOracle │
│  Gas Prices │               │   Contract  │
└─────────────┘               └─────────────┘
       │                              │
       │                              ▼
       │                      ┌─────────────┐
       │                      │  Aggregate  │
       │                      │   & Store   │
       │                      └─────────────┘
       │                              │
       ▼                              ▼
┌─────────────┐               ┌─────────────┐
│  Use for    │◀──────────────│   Provide   │
│  Estimation │               │   Gas Data  │
└─────────────┘               └─────────────┘

Reporting Process

1. Each Maintainer observes gas prices on external chains

2. Maintainers periodically report observations to GasOracle contract

3. Contract aggregates reports, using median value for consensus

4. Aggregated gas prices stored on-chain for cross-chain fee calculation

Aggregation Method

The oracle uses median aggregation to resist manipulation:

• Collects reports from multiple Maintainers

• Sorts reported values

• Takes median as the consensus price

• Updates only when sufficient reports received

Cross-chain Fee Calculation

Fee Components

Component	Description
Target chain gas	Estimated execution cost on target chain
Protocol fee	Fee for protocol operation and LP rewards
Buffer	Safety margin for gas price fluctuations

Calculation Flow

User Request ──▶ Estimate Target Gas ──▶ Add Protocol Fee ──▶ Apply Buffer ──▶ Final Fee
      │                  │                      │                  │              │
      ▼                  ▼                      ▼                  ▼              ▼
  Source chain     GasOracle data         Configurable        Percentage      Deducted from
  amount           + operation type       per chain           multiplier      transfer amount

Fee Deduction

Cross-chain fees are deducted from the transfer amount:

• User sends X tokens on source chain

• Fee F is calculated based on target chain costs

• User receives (X - F) tokens on target chain

Gas Price Updates

Update Triggers

Trigger	Description
Block interval	Regular updates every N blocks
Price deviation	Update when price changes > threshold
Manual override	Emergency updates by governance

Staleness Protection

The system includes staleness checks:

• Gas prices have a maximum age

• Stale prices trigger warnings or fallback to defaults

• Critical operations may be paused if gas data too old

Chain-specific Considerations

EVM Chains

• Support EIP-1559 fee model (base fee + priority fee)

• Dynamic base fee adjustment based on network congestion

• Priority fee for transaction ordering preference

Bitcoin-like Chains

• Fee rate in satoshis per virtual byte

• UTXO-based transaction size estimation

• Replace-By-Fee (RBF) support for stuck transactions

Other Chains

Each chain type may have unique gas/fee models:

Chain Type	Fee Model
Solana	Compute units + priority fee
NEAR	Gas units with conversion rate
TON	Gas units with forwarding fees

Configuration Parameters

Parameter	Description	Default
gas_cache_blocks	Blocks to cache for averaging	20
gas_price_resolution	Minimum gas price unit	Chain-specific
max_gas_tip_percentage	Max tip as % of base	25%
gas_update_interval	Blocks between updates	10
gas_staleness_threshold	Max age before stale	100 blocks