add get_lower_bound_sqrt_k functor

drift-labs · Jan 26, 2024 · 0508beb · 0508beb
1 parent 0960a14
commit 0508beb
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Showing 3 changed files with 24 additions and 15 deletions.
diff --git a/programs/drift/src/controller/position/tests.rs b/programs/drift/src/controller/position/tests.rs
@@ -1578,6 +1578,12 @@ fn recenter_amm_2() {
     let current_k = perp_market.amm.sqrt_k;
     let _current_peg = perp_market.amm.peg_multiplier;
     let new_k = current_k * 2;
+
+    // refusal to decrease further
+    assert_eq!(current_k, current_k);
+    assert_eq!(perp_market.amm.user_lp_shares, current_k - 1);
+    assert_eq!(perp_market.amm.get_lower_bound_sqrt_k().unwrap(), current_k);
+
     recenter_perp_market_amm(&mut perp_market.amm, oracle_price_data.price as u128, new_k).unwrap();
 
     assert_eq!(perp_market.amm.sqrt_k, new_k);
@@ -1611,8 +1617,15 @@ fn recenter_amm_2() {
     assert_eq!(adjustment_cost, 0);
 
     update_k(&mut perp_market, &update_k_result).unwrap();
-    assert_eq!(perp_market.amm.sqrt_k, new_sqrt_k);
 
+    // higher lower bound now
+    assert_eq!(perp_market.amm.sqrt_k, new_sqrt_k);
+    assert_eq!(perp_market.amm.user_lp_shares, current_k - 1);
+    assert!(perp_market.amm.get_lower_bound_sqrt_k().unwrap() > current_k);
+    assert_eq!(
+        perp_market.amm.get_lower_bound_sqrt_k().unwrap(),
+        140766081456000000
+    );
     // assert_eq!(perp_market.amm.peg_multiplier, current_peg);
 }
 

diff --git a/programs/drift/src/math/repeg.rs b/programs/drift/src/math/repeg.rs
@@ -285,20 +285,7 @@ pub fn adjust_amm(
             // TODO can be off by 1?
 
             // always let protocol-owned sqrt_k be either least .1% of lps or the base amount / min order
-            let new_sqrt_k_lower_bound = market.amm.sqrt_k.min(
-                market
-                    .amm
-                    .user_lp_shares
-                    .safe_add(market.amm.user_lp_shares.safe_div(1000)?)?
-                    .max(market.amm.min_order_size.cast()?)
-                    .max(
-                        market
-                            .amm
-                            .base_asset_amount_with_amm
-                            .unsigned_abs()
-                            .cast()?,
-                    ),
-            );
+            let new_sqrt_k_lower_bound = market.amm.get_lower_bound_sqrt_k()?;
 
             let new_sqrt_k = market
                 .amm

diff --git a/programs/drift/src/state/perp_market.rs b/programs/drift/src/state/perp_market.rs
@@ -826,6 +826,15 @@ impl AMM {
         }
     }
 
+    pub fn get_lower_bound_sqrt_k(self) -> DriftResult<u128> {
+        Ok(self.sqrt_k.min(
+            self.user_lp_shares
+                .safe_add(self.user_lp_shares.safe_div(1000)?)?
+                .max(self.min_order_size.cast()?)
+                .max(self.base_asset_amount_with_amm.unsigned_abs().cast()?),
+        ))
+    }
+
     pub fn get_protocol_owned_position(self) -> DriftResult<i64> {
         self.base_asset_amount_with_amm
             .safe_add(self.base_asset_amount_with_unsettled_lp)?