Fix/per 1k estimate always zero (#1152)

* add fix for return per 1k

* extract helper and add test

Author: camfairchild

pallets/subtensor/src/rpc_info/delegate_info.rs

@@ -21,6 +21,34 @@ pub struct DelegateInfo<T: Config> {
 }
 
 impl<T: Config> Pallet<T> {
+    fn return_per_1000_tao(
+        take: Compact<u16>,
+        total_stake: U64F64,
+        emissions_per_day: U64F64,
+    ) -> U64F64 {
+        // Get the take as a percentage and subtract it from 1 for remainder.
+        let without_take: U64F64 = U64F64::from_num(1)
+            .saturating_sub(U64F64::from_num(take.0).saturating_div(u16::MAX.into()));
+
+        if total_stake > U64F64::from_num(0) {
+            emissions_per_day
+                .saturating_mul(without_take)
+                // Divide by 1000 TAO for return per 1k
+                .saturating_div(total_stake.saturating_div(U64F64::from_num(1000.0 * 1e9)))
+        } else {
+            U64F64::from_num(0)
+        }
+    }
+
+    #[cfg(test)]
+    pub fn return_per_1000_tao_test(
+        take: Compact<u16>,
+        total_stake: U64F64,
+        emissions_per_day: U64F64,
+    ) -> U64F64 {
+        Self::return_per_1000_tao(take, total_stake, emissions_per_day)
+    }
+
     fn get_delegate_by_existing_account(delegate: AccountIdOf<T>) -> DelegateInfo<T> {
         let mut nominators = Vec::<(T::AccountId, Compact<u64>)>::new();
 
@@ -63,14 +91,8 @@ impl<T: Config> Pallet<T> {
         let total_stake: U64F64 =
             Self::get_stake_for_hotkey_on_subnet(&delegate.clone(), Self::get_root_netuid()).into();
 
-        let return_per_1000: U64F64 = if total_stake > U64F64::from_num(0) {
-            emissions_per_day
-                .saturating_mul(u16::MAX.saturating_sub(take.0).into())
-                .saturating_div(u16::MAX.into())
-                .saturating_div(total_stake.saturating_div(U64F64::from_num(1000)))
-        } else {
-            U64F64::from_num(0)
-        };
+        let return_per_1000: U64F64 =
+            Self::return_per_1000_tao(take, total_stake, emissions_per_day);
 
         DelegateInfo {
             delegate_ss58: delegate.clone(),

pallets/subtensor/src/tests/delegate_info.rs

@@ -0,0 +1,33 @@
+use codec::Compact;
+use substrate_fixed::types::U64F64;
+
+use super::mock::*;
+
+#[test]
+fn test_return_per_1000_tao() {
+    let take = // 18% take to the Validator
+        Compact::<u16>::from((U64F64::from_num(0.18 * u16::MAX as f64)).saturating_to_num::<u16>());
+
+    // 10_000 TAO total validator stake
+    let total_stake = U64F64::from_num(10_000.0 * 1e9);
+    // 1000 TAO emissions per day
+    let emissions_per_day = U64F64::from_num(1000.0 * 1e9);
+
+    let return_per_1000 =
+        SubtensorModule::return_per_1000_tao_test(take, total_stake, emissions_per_day);
+
+    // We expect 82 TAO per day with 10% of total_stake
+    let expected_return_per_1000 = U64F64::from_num(82.0);
+
+    let diff_from_expected: f64 = (return_per_1000 / U64F64::from_num(1e9))
+        .saturating_sub(expected_return_per_1000)
+        .to_num::<f64>();
+
+    let eps: f64 = 0.0005e9; // Precision within 0.0005 TAO
+    assert!(
+        diff_from_expected.abs() <= eps,
+        "Difference from expected: {} is greater than precision: {}",
+        diff_from_expected,
+        eps
+    );
+}

pallets/subtensor/src/tests/mod.rs

@@ -1,6 +1,7 @@
 mod batch_tx;
 mod children;
 mod coinbase;
+mod delegate_info;
 mod difficulty;
 mod emission;
 mod epoch;