Merge pull request #1758 from backend-developers-ltd/steep

sigmoid steepness adjustment

Author: sam0x17

docs/img/sigmoid_steepness.png

@@ -7,7 +7,7 @@ TxRateLimit: u64 = 1; // [1 @ 64,888]
 ### netuid 1 (text_prompting)
 ```rust
 Rho: u16 = 10;
-AlphaSigmoidSteepness: u16 = 10.0
+AlphaSigmoidSteepness: i16 = 1000
 Kappa: u16 = 32_767; // 0.5 = 65535/2
 MaxAllowedUids: u16 = 1024;
 Issuance: u64 = 0;
@@ -48,7 +48,7 @@ WeightsSetRateLimit: u64 = 100;
 ### netuid 3 (causallmnext)
 ```rust
 Rho: u16 = 10;
-AlphaSigmoidSteepness: u16 = 10.0
+AlphaSigmoidSteepness: i16 = 1000
 Kappa: u16 = 32_767; // 0.5 = 65535/2
 MaxAllowedUids: u16 = 4096;
 Issuance: u64 = 0;

hyperparameters.md

@@ -105,6 +105,8 @@ pub mod pallet {
         MaxAllowedUIdsLessThanCurrentUIds,
         /// The maximum value for bonds moving average is reached
         BondsMovingAverageMaxReached,
+        /// Only root can set negative sigmoid steepness values
+        NegativeSigmoidSteepness,
     }
     /// Enum for specifying the type of precompile operation.
     #[derive(Encode, Decode, TypeInfo, Clone, PartialEq, Eq, Debug, Copy)]
@@ -1560,20 +1562,36 @@ pub mod pallet {
         /// # Arguments
         /// * `origin` - The origin of the call, which must be the root account.
         /// * `netuid` - The unique identifier for the subnet.
-        /// * `steepness` - The new steepness for the alpha sigmoid function.
+        /// * `steepness` - The Steepness for the alpha sigmoid function. (range is 0-int16::MAX,
+        /// negative values are reserved for future use)
         ///
         /// # Errors
         /// * `BadOrigin` - If the caller is not the root account.
+        /// * `SubnetDoesNotExist` - If the specified subnet does not exist.
+        /// * `NegativeSigmoidSteepness` - If the steepness is negative and the caller is
+        /// root.
         /// # Weight
         /// Weight is handled by the `#[pallet::weight]` attribute.
         #[pallet::call_index(68)]
         #[pallet::weight((0, DispatchClass::Operational, Pays::No))]
         pub fn sudo_set_alpha_sigmoid_steepness(
             origin: OriginFor<T>,
             netuid: NetUid,
-            steepness: u16,
+            steepness: i16,
         ) -> DispatchResult {
-            ensure_root(origin)?;
+            pallet_subtensor::Pallet::<T>::ensure_subnet_owner_or_root(origin.clone(), netuid)?;
+
+            ensure!(
+                pallet_subtensor::Pallet::<T>::if_subnet_exist(netuid),
+                Error::<T>::SubnetDoesNotExist
+            );
+
+            let is_root = ensure_root(origin).is_ok();
+            ensure!(
+                is_root || steepness >= 0,
+                Error::<T>::NegativeSigmoidSteepness
+            );
+
             pallet_subtensor::Pallet::<T>::set_alpha_sigmoid_steepness(netuid, steepness);
 
             log::debug!(

pallets/admin-utils/src/lib.rs

@@ -82,7 +82,7 @@ parameter_types! {
     pub const TransactionByteFee: Balance = 100;
     pub const SDebug:u64 = 1;
     pub const InitialRho: u16 = 30;
-    pub const InitialAlphaSigmoidSteepness: u16 = 10;
+    pub const InitialAlphaSigmoidSteepness: i16 = 1000;
     pub const InitialKappa: u16 = 32_767;
     pub const InitialTempo: u16 = 0;
     pub const SelfOwnership: u64 = 2;

pallets/admin-utils/src/tests/mock.rs

@@ -1146,6 +1146,65 @@ fn test_sudo_set_liquid_alpha_enabled() {
     });
 }
 
+#[test]
+fn test_sudo_set_alpha_sigmoid_steepness() {
+    new_test_ext().execute_with(|| {
+        let netuid = NetUid::from(1);
+        let to_be_set: i16 = 5000;
+        add_network(netuid, 10);
+        let init_value = SubtensorModule::get_alpha_sigmoid_steepness(netuid);
+        assert_eq!(
+            AdminUtils::sudo_set_alpha_sigmoid_steepness(
+                <<Test as Config>::RuntimeOrigin>::signed(U256::from(1)),
+                netuid,
+                to_be_set
+            ),
+            Err(DispatchError::BadOrigin)
+        );
+        assert_eq!(
+            AdminUtils::sudo_set_alpha_sigmoid_steepness(
+                <<Test as Config>::RuntimeOrigin>::root(),
+                netuid.next(),
+                to_be_set
+            ),
+            Err(Error::<Test>::SubnetDoesNotExist.into())
+        );
+
+        let owner = U256::from(10);
+        pallet_subtensor::SubnetOwner::<Test>::insert(netuid, owner);
+        assert_eq!(
+            AdminUtils::sudo_set_alpha_sigmoid_steepness(
+                <<Test as Config>::RuntimeOrigin>::signed(owner),
+                netuid,
+                -to_be_set
+            ),
+            Err(Error::<Test>::NegativeSigmoidSteepness.into())
+        );
+        assert_eq!(
+            SubtensorModule::get_alpha_sigmoid_steepness(netuid),
+            init_value
+        );
+        assert_ok!(AdminUtils::sudo_set_alpha_sigmoid_steepness(
+            <<Test as Config>::RuntimeOrigin>::root(),
+            netuid,
+            to_be_set
+        ));
+        assert_eq!(
+            SubtensorModule::get_alpha_sigmoid_steepness(netuid),
+            to_be_set
+        );
+        assert_ok!(AdminUtils::sudo_set_alpha_sigmoid_steepness(
+            <<Test as Config>::RuntimeOrigin>::root(),
+            netuid,
+            -to_be_set
+        ));
+        assert_eq!(
+            SubtensorModule::get_alpha_sigmoid_steepness(netuid),
+            -to_be_set
+        );
+    });
+}
+
 #[test]
 fn test_set_alpha_values_dispatch_info_ok() {
     new_test_ext().execute_with(|| {

pallets/admin-utils/src/tests/mod.rs

@@ -1298,10 +1298,9 @@ impl<T: Config> Pallet<T> {
         // sigmoid = 1. / (1. + e^(-steepness * (combined_diff - 0.5)))
         let sigmoid = one.saturating_div(
             one.saturating_add(safe_exp(
-                I32F32::from_num(-1).saturating_mul(
-                    alpha_sigmoid_steepness
-                        .saturating_mul(combined_diff.saturating_sub(I32F32::from_num(0.5))),
-                ),
+                alpha_sigmoid_steepness
+                    .saturating_div(I32F32::from_num(-100))
+                    .saturating_mul(combined_diff.saturating_sub(I32F32::from_num(0.5))),
             )),
         );
         let alpha =

pallets/subtensor/src/epoch/run_epoch.rs

@@ -599,7 +599,7 @@ pub mod pallet {
     }
     #[pallet::type_value]
     /// Default value for alpha sigmoid steepness.
-    pub fn DefaultAlphaSigmoidSteepness<T: Config>() -> u16 {
+    pub fn DefaultAlphaSigmoidSteepness<T: Config>() -> i16 {
         T::InitialAlphaSigmoidSteepness::get()
     }
     #[pallet::type_value]
@@ -1296,7 +1296,7 @@ pub mod pallet {
     #[pallet::storage]
     /// --- MAP ( netuid ) --> AlphaSigmoidSteepness
     pub type AlphaSigmoidSteepness<T> =
-        StorageMap<_, Identity, NetUid, u16, ValueQuery, DefaultAlphaSigmoidSteepness<T>>;
+        StorageMap<_, Identity, NetUid, i16, ValueQuery, DefaultAlphaSigmoidSteepness<T>>;
     #[pallet::storage]
     /// --- MAP ( netuid ) --> Kappa
     pub type Kappa<T> = StorageMap<_, Identity, NetUid, u16, ValueQuery, DefaultKappa<T>>;

pallets/subtensor/src/lib.rs

@@ -107,7 +107,7 @@ mod config {
         type InitialRho: Get<u16>;
         /// AlphaSigmoidSteepness constant.
         #[pallet::constant]
-        type InitialAlphaSigmoidSteepness: Get<u16>;
+        type InitialAlphaSigmoidSteepness: Get<i16>;
         /// Kappa constant.
         #[pallet::constant]
         type InitialKappa: Get<u16>;

pallets/subtensor/src/macros/config.rs

@@ -51,7 +51,7 @@ mod events {
         /// Rho value is set.
         RhoSet(NetUid, u16),
         /// steepness of the sigmoid used to compute alpha values.
-        AlphaSigmoidSteepnessSet(NetUid, u16),
+        AlphaSigmoidSteepnessSet(NetUid, i16),
         /// Kappa is set for a subnet.
         KappaSet(NetUid, u16),
         /// minimum allowed weight is set for a subnet.

pallets/subtensor/src/macros/events.rs

@@ -2644,7 +2644,7 @@ fn setup_yuma_3_scenario(netuid: NetUid, n: u16, sparse: bool, max_stake: u64, s
     SubtensorModule::set_min_allowed_weights(netuid, 1);
     SubtensorModule::set_max_weight_limit(netuid, u16::MAX);
     SubtensorModule::set_bonds_penalty(netuid, 0);
-    SubtensorModule::set_alpha_sigmoid_steepness(netuid, 10);
+    SubtensorModule::set_alpha_sigmoid_steepness(netuid, 1000);
     SubtensorModule::set_bonds_moving_average(netuid, 975_000);
 
     // === Register