feat(rug): fractional powers without roots

Author: cong-or

src/audit/src/offline/bin/main.rs

@@ -40,6 +40,9 @@ pub struct Args {
     /// Gamma value for Quadratic scaling
     #[clap(short, long)]
     gamma: Option<String>,
+    /// Rounding precision for arithmetic
+    #[clap(short, long)]
+    precision: Option<String>,
 }
 
 fn main() -> Result<(), Box<dyn Error>> {
@@ -70,6 +73,11 @@ fn main() -> Result<(), Box<dyn Error>> {
         std::env::set_var(GAMMA, gamma);
     }
 
+    if let Some(precision) = args.precision {
+        const PRECISION: &str = "QUADRATIC_VOTING_PRECISION";
+        std::env::set_var(PRECISION, precision);
+    }
+
     // Load and replay fund fragments from storage
     let storage_path = PathBuf::from(args.fragments);
 

src/chain-libs/chain-impl-mockchain/src/vote/tally.rs

@@ -191,12 +191,14 @@ impl TallyResult {
             let numer = gamma.numer();
 
             let stake = Float::with_val(precision, weight.0);
-            // r = gamma in rational form
-            let exp_r = Rational::from((*numer, *denom));
-            let exp_f = Float::with_val(precision, &exp_r);
-            let p = stake.clone().pow(&exp_f);
 
-            let weight = p
+            // rational = gamma in rational form i.e fraction
+            // 0.5 = 1/2
+            let gamma = Float::with_val(precision, &Rational::from((*numer, *denom)));
+
+            let stake_with_gamma_scaling = stake.clone().pow(&gamma);
+
+            let weight = stake_with_gamma_scaling
                 .to_integer_round(Round::Down)
                 .unwrap_or((Integer::from(weight.0), Ordering::Less))
                 .0

src/chain-libs/chain-vote/src/tally.rs

@@ -183,13 +183,18 @@ impl EncryptedTally {
         let numer = gamma.numer();
 
         let stake = Float::with_val(precision, weight);
-        // r = gamma in rational form
-        let exp_r = Rational::from((*numer, *denom));
-        let exp_f = Float::with_val(precision, &exp_r);
-        let p = stake.clone().pow(&exp_f);
-        info!("{} to the power of {} is: {}", stake, exp_f, p);
 
-        let weight = p
+        // rational = gamma in rational form i.e fraction
+        // 0.5 = 1/2
+        let gamma = Float::with_val(precision, &Rational::from((*numer, *denom)));
+
+        let stake_with_gamma_scaling = stake.clone().pow(&gamma);
+        info!(
+            "{} to the power of {} is: {}",
+            stake, gamma, stake_with_gamma_scaling
+        );
+
+        let weight = stake_with_gamma_scaling
             .to_integer_round(Round::Down)
             .unwrap_or((Integer::from(weight), Ordering::Less))
             .0