Alpha injection cap

pallets/subtensor/src/coinbase/run_coinbase.rs

@@ -124,6 +124,11 @@ impl<T: Config> Pallet<T> {
         let mut alpha_in: BTreeMap<NetUid, U96F32> = BTreeMap::new();
         let mut alpha_out: BTreeMap<NetUid, U96F32> = BTreeMap::new();
         let mut excess_tao: BTreeMap<NetUid, U96F32> = BTreeMap::new();
+        let tao_block_emission: U96F32 = U96F32::saturating_from_num(
+            Self::get_block_emission()
+                .unwrap_or(TaoCurrency::ZERO)
+                .to_u64(),
+        );
 
         // Only calculate for subnets that we are emitting to.
         for (&netuid_i, &tao_emission_i) in subnet_emissions.iter() {
@@ -142,8 +147,9 @@ impl<T: Config> Pallet<T> {
             let alpha_out_i: U96F32 = alpha_emission_i;
             let mut alpha_in_i: U96F32 = tao_emission_i.safe_div_or(price_i, U96F32::from_num(0.0));
 
-            if alpha_in_i > alpha_emission_i {
-                alpha_in_i = alpha_emission_i;
+            let alpha_injection_cap: U96F32 = alpha_emission_i.min(tao_block_emission);
+            if alpha_in_i > alpha_injection_cap {
+                alpha_in_i = alpha_injection_cap;
                 tao_in_i = alpha_in_i.saturating_mul(price_i);
             }
 

pallets/subtensor/src/tests/coinbase.rs

@@ -3919,3 +3919,39 @@ fn test_pending_emission_start_call_not_done() {
         );
     });
 }
+
+#[test]
+fn test_get_subnet_terms_alpha_emissions_cap() {
+    new_test_ext(1).execute_with(|| {
+        let owner_hotkey = U256::from(10);
+        let owner_coldkey = U256::from(11);
+        let netuid = add_dynamic_network(&owner_hotkey, &owner_coldkey);
+        let tao_block_emission: U96F32 = U96F32::saturating_from_num(
+            SubtensorModule::get_block_emission()
+                .unwrap_or(TaoCurrency::ZERO)
+                .to_u64(),
+        );
+
+        // price = 1.0
+        // tao_block_emission = 1000000000
+        // tao_block_emission == alpha_emission_i
+        // alpha_in_i <= alpha_injection_cap
+        let emissions1 = U96F32::from_num(100_000_000);
+
+        let subnet_emissions1 = BTreeMap::from([(netuid, emissions1)]);
+        let (_, alpha_in, _, _) = SubtensorModule::get_subnet_terms(&subnet_emissions1);
+
+        assert_eq!(alpha_in.get(&netuid).copied().unwrap(), emissions1);
+
+        // price = 1.0
+        // tao_block_emission = 1000000000
+        // tao_block_emission == alpha_emission_i
+        // alpha_in_i > alpha_injection_cap
+        let emissions2 = U96F32::from_num(10_000_000_000u64);
+
+        let subnet_emissions2 = BTreeMap::from([(netuid, emissions2)]);
+        let (_, alpha_in, _, _) = SubtensorModule::get_subnet_terms(&subnet_emissions2);
+
+        assert_eq!(alpha_in.get(&netuid).copied().unwrap(), tao_block_emission);
+    });
+}

runtime/src/lib.rs

@@ -237,7 +237,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
     //   `spec_version`, and `authoring_version` are the same between Wasm and native.
     // This value is set to 100 to notify Polkadot-JS App (https://polkadot.js.org/apps) to use
     //   the compatible custom types.
-    spec_version: 361,
+    spec_version: 362,
     impl_version: 1,
     apis: RUNTIME_API_VERSIONS,
     transaction_version: 1,