116 lines
4.2 KiB
Rust
116 lines
4.2 KiB
Rust
use super::GasEscalator;
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use ethers_core::types::U256;
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/// Geometrically increasing gas price.
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///
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/// Start with `initial_price`, then increase it every 'every_secs' seconds by a fixed coefficient.
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/// Coefficient defaults to 1.125 (12.5%), the minimum increase for Parity to replace a transaction.
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/// Coefficient can be adjusted, and there is an optional upper limit.
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///
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/// https://github.com/makerdao/pymaker/blob/master/pymaker/gas.py#L168
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#[derive(Clone, Debug)]
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pub struct GeometricGasPrice {
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every_secs: u64,
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coefficient: f64,
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max_price: Option<U256>,
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}
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impl GeometricGasPrice {
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/// Constructor
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///
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/// Note: Providing `None` to `max_price` requires giving it a type-hint, so you'll need
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/// to call this like `GeometricGasPrice::new(1.125, 60u64, None::<u64>)`.
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pub fn new<T: Into<U256>, K: Into<u64>>(
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coefficient: f64,
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every_secs: K,
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max_price: Option<T>,
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) -> Self {
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GeometricGasPrice {
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every_secs: every_secs.into(),
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coefficient,
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max_price: max_price.map(Into::into),
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}
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}
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}
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impl GasEscalator for GeometricGasPrice {
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fn get_gas_price(&self, initial_price: U256, time_elapsed: u64) -> U256 {
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let mut result = initial_price.as_u64() as f64;
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if time_elapsed >= self.every_secs {
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let iters = time_elapsed / self.every_secs;
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for _ in 0..iters {
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result *= self.coefficient;
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}
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}
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let mut result = U256::from(result.ceil() as u64);
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if let Some(max_price) = self.max_price {
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result = std::cmp::min(result, max_price);
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}
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result
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}
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}
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#[cfg(test)]
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// https://github.com/makerdao/pymaker/blob/master/tests/test_gas.py#L165
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mod tests {
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use super::*;
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#[test]
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fn gas_price_increases_with_time() {
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let oracle = GeometricGasPrice::new(1.125, 10u64, None::<u64>);
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let initial_price = U256::from(100);
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assert_eq!(oracle.get_gas_price(initial_price, 0), 100.into());
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assert_eq!(oracle.get_gas_price(initial_price, 1), 100.into());
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assert_eq!(oracle.get_gas_price(initial_price, 10), 113.into());
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assert_eq!(oracle.get_gas_price(initial_price, 15), 113.into());
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assert_eq!(oracle.get_gas_price(initial_price, 20), 127.into());
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assert_eq!(oracle.get_gas_price(initial_price, 30), 143.into());
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assert_eq!(oracle.get_gas_price(initial_price, 50), 181.into());
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assert_eq!(oracle.get_gas_price(initial_price, 100), 325.into());
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}
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#[test]
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fn gas_price_should_obey_max_value() {
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let oracle = GeometricGasPrice::new(1.125, 60u64, Some(2500));
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let initial_price = U256::from(1000);
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assert_eq!(oracle.get_gas_price(initial_price, 0), 1000.into());
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assert_eq!(oracle.get_gas_price(initial_price, 1), 1000.into());
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assert_eq!(oracle.get_gas_price(initial_price, 59), 1000.into());
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assert_eq!(oracle.get_gas_price(initial_price, 60), 1125.into());
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assert_eq!(oracle.get_gas_price(initial_price, 119), 1125.into());
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assert_eq!(oracle.get_gas_price(initial_price, 120), 1266.into());
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assert_eq!(oracle.get_gas_price(initial_price, 1200), 2500.into());
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assert_eq!(oracle.get_gas_price(initial_price, 3000), 2500.into());
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assert_eq!(oracle.get_gas_price(initial_price, 1000000), 2500.into());
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}
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#[test]
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#[allow(clippy::float_cmp)]
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fn behaves_with_realistic_values() {
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let oracle = GeometricGasPrice::new(1.25, 10u64, None::<u64>);
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const GWEI: f64 = 1000000000.0;
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let initial_price = U256::from(100 * GWEI as u64);
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for seconds in &[0u64, 1, 10, 12, 30, 60] {
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println!(
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"gas price after {} seconds is {}",
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seconds,
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oracle.get_gas_price(initial_price, *seconds).as_u64() as f64 / GWEI
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);
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}
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let normalized = |time| oracle.get_gas_price(initial_price, time).as_u64() as f64 / GWEI;
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assert_eq!(normalized(0), 100.0);
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assert_eq!(normalized(1), 100.0);
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assert_eq!(normalized(10), 125.0);
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assert_eq!(normalized(12), 125.0);
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assert_eq!(normalized(30), 195.3125);
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assert_eq!(normalized(60), 381.469726563);
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}
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}
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