Merge pull request #4126 from nymtech/chore/adjust-selection-weights

using performance^20 when calculating active set selection weight

common/cosmwasm-smart-contracts/contracts-common/src/types.rs

@@ -3,6 +3,7 @@
 
 use cosmwasm_schema::cw_serde;
 use cosmwasm_std::Decimal;
+use cosmwasm_std::OverflowError;
 use cosmwasm_std::Uint128;
 use serde::de::Error;
 use serde::{Deserialize, Deserializer};
@@ -71,6 +72,10 @@ impl Percent {
         // we know the cast from u128 to u8 is a safe one since the internal value must be within 0 - 1 range
         truncate_decimal(hundred * self.0).u128() as u8
     }
+
+    pub fn checked_pow(&self, exp: u32) -> Result<Self, OverflowError> {
+        self.0.checked_pow(exp).map(Percent)
+    }
 }
 
 impl Display for Percent {

nym-api/src/epoch_operations/rewarded_set_assignment.rs

@@ -24,7 +24,15 @@ struct MixnodeWithStakeAndPerformance {
 
 impl MixnodeWithStakeAndPerformance {
     fn to_selection_weight(&self) -> f64 {
-        let scaled_stake = self.total_stake * self.performance;
+        let scaled_performance = match self.performance.checked_pow(20) {
+            Ok(perf) => perf,
+            Err(overflow) => {
+                warn!("the node's performance ({}) has overflow while scaling it by the factor of 20: {overflow}. Setting it to 0 instead.", self.performance);
+                return 0.;
+            }
+        };
+
+        let scaled_stake = self.total_stake * scaled_performance;
         stake_to_f64(scaled_stake)
     }
 }