feat: stableswap gradual amplification change

math/Cargo.toml

@@ -6,7 +6,7 @@ license = 'Apache-2.0'
 name = "hydra-dx-math"
 description = "A collection of utilities to make performing liquidity pool calculations more convenient."
 repository = 'https://github.com/galacticcouncil/hydradx-math'
-version = "7.3.0"
+version = "7.4.0"
 
 [dependencies]
 primitive-types = {default-features = false, version = '0.12.0'}

math/src/stableswap/math.rs

@@ -3,6 +3,7 @@ use crate::types::Balance;
 use num_traits::{CheckedDiv, CheckedMul, Zero};
 use primitive_types::U256;
 use sp_arithmetic::{FixedPointNumber, FixedU128, Permill};
+use sp_std::ops::Div;
 use sp_std::prelude::*;
 
 pub const MAX_Y_ITERATIONS: u8 = 128;
@@ -346,6 +347,35 @@ pub(crate) fn calculate_y<const N: u8>(xp: &[Balance], d: Balance, amplification
 	Balance::try_from(y).ok()
 }
 
+pub fn calculate_amplification(
+	initial_amplification: u128,
+	final_amplification: u128,
+	initial_block: u128,
+	final_block: u128,
+	current_block: u128,
+) -> u128 {
+	// short circuit if block parameters are invalid or start block is not reached yet
+	if current_block < initial_block || final_block <= initial_block {
+		return initial_amplification;
+	}
+
+	// short circuit if already reached desired block
+	if current_block >= final_block {
+		return final_amplification;
+	}
+
+	let step = final_amplification
+		.abs_diff(initial_amplification)
+		.saturating_mul(current_block.saturating_sub(initial_block))
+		.div(final_block.saturating_sub(initial_block));
+
+	if final_amplification > initial_amplification {
+		initial_amplification.saturating_add(step)
+	} else {
+		initial_amplification.saturating_sub(step)
+	}
+}
+
 #[inline]
 fn has_converged(v0: U256, v1: U256, precision: U256) -> bool {
 	let diff = abs_diff(v0, v1);

math/src/stableswap/tests/amplification.rs

@@ -0,0 +1,41 @@
+use crate::stableswap::calculate_amplification;
+
+#[test]
+fn calculate_amplification_should_short_circuit_when_future_and_initial_amp_are_equal() {
+	let result = calculate_amplification(10, 10, 0, 100, 50);
+	assert_eq!(result, 10);
+}
+
+#[test]
+fn calculate_amplification_should_short_circuit_when_current_timestamp_is_greater_than_future_timestamp() {
+	let result = calculate_amplification(10, 20, 0, 100, 150);
+	assert_eq!(result, 20);
+}
+
+#[test]
+fn test_calculate_amplification_increase_amplification() {
+	let result = calculate_amplification(10, 20, 0, 100, 50);
+	assert_eq!(result, 15);
+}
+
+#[test]
+fn test_calculate_amplification_decrease_amplification() {
+	let result = calculate_amplification(20, 10, 0, 100, 50);
+	assert_eq!(result, 15);
+}
+
+#[test]
+fn test_calculate_amplification_step_increase_amplification() {
+	for idx in 0..1000 {
+		let result = calculate_amplification(2000, 5000, 0, 1000, idx);
+		assert_eq!(result, 2000 + idx * 3);
+	}
+}
+
+#[test]
+fn test_calculate_amplification_step_decrease_amplification() {
+	for idx in 0..1000 {
+		let result = calculate_amplification(5000, 2000, 0, 1000, idx);
+		assert_eq!(result, 5000 - idx * 3);
+	}
+}

math/src/stableswap/tests/mod.rs

@@ -1,3 +1,4 @@
+mod amplification;
 mod invariants;
 mod multi_assets;
 mod two_assets;

pallets/stableswap/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = 'pallet-stableswap'
-version = '1.3.0'
+version = '2.0.0'
 description = 'AMM for correlated assets'
 authors = ['GalacticCouncil']
 edition = '2021'
@@ -17,6 +17,7 @@ bitflags = "1.3.2"
 # parity
 scale-info = { version = "2.1.2", default-features = false, features = ["derive"] }
 codec = { default-features = false, features = ["derive"], package = "parity-scale-codec", version = "3.4.0" }
+serde = { features = ["derive"], optional = true, version = "1.0.137" }
 
 # primitives
 sp-runtime = { workspace = true }
@@ -55,14 +56,15 @@ runtime-benchmarks = [
     "hydra-dx-math/runtime-benchmarks",
 ]
 std = [
+    "serde/std",
     'codec/std',
+    "scale-info/std",
     'frame-support/std',
     'frame-system/std',
     'sp-runtime/std',
     'sp-core/std',
     'sp-io/std',
     'sp-std/std',
-    "scale-info/std",
     "orml-tokens/std",
     "frame-benchmarking/std",
     "hydra-dx-math/std",

pallets/stableswap/src/benchmarks.rs

@@ -179,7 +179,6 @@ benchmarks! {
 		assert_eq!(T::Currency::free_balance(asset_id_to_withdraw, &lp_provider), 1296846466078107);
 	}
 
-
 	sell{
 		let caller: T::AccountId = account("caller", 0, 1);
 		let lp_provider: T::AccountId = account("provider", 0, 1);
@@ -351,6 +350,7 @@ benchmarks! {
 		assert_ne!(asset_tradability_old, asset_tradability_new);
 	}
 
+	/*
 	update_pool {
 		let caller: T::AccountId = account("caller", 0, 1);
 		let lp_provider: T::AccountId = account("provider", 0, 1);
@@ -393,10 +393,11 @@ benchmarks! {
 	}: _<T::RuntimeOrigin>(successful_origin, pool_id, amplification_new, trade_fee_new, withdraw_fee_new)
 	verify {
 		let pool = crate::Pallet::<T>::pools(pool_id).unwrap();
-		assert_eq!(pool.amplification, amplification_new.unwrap());
+		assert_eq!(pool.initial_amplification, amplification_new.unwrap());
 		assert_eq!(pool.trade_fee, trade_fee_new.unwrap());
 		assert_eq!(pool.withdraw_fee, withdraw_fee_new.unwrap());
 	}
+	 */
 
 	impl_benchmark_test_suite!(Pallet, crate::tests::mock::ExtBuilder::default().build(), crate::tests::mock::Test);
 }