Ensure stake threshold is respected when handing out vpermits

pallets/subtensor/src/epoch/math.rs

@@ -246,6 +246,22 @@ pub fn is_topk(vector: &[I32F32], k: usize) -> Vec<bool> {
     result
 }
 
+// Returns a bool vector where an item is true if the vector item is in topk values and is non-zero.
+#[allow(dead_code, clippy::indexing_slicing)]
+pub fn is_topk_nonzero(vector: &[I32F32], k: usize) -> Vec<bool> {
+    let n: usize = vector.len();
+    let mut result: Vec<bool> = vector.iter().map(|&elem| elem != I32F32::from(0)).collect();
+    if n < k {
+        return result;
+    }
+    let mut idxs: Vec<usize> = (0..n).collect();
+    idxs.sort_by_key(|&idx| &vector[idx]); // ascending stable sort
+    for &idx in idxs.iter().take(n.saturating_sub(k)) {
+        result[idx] = false;
+    }
+    result
+}
+
 // Returns a normalized (sum to 1 except 0) copy of the input vector.
 #[allow(dead_code)]
 pub fn normalize(x: &[I32F32]) -> Vec<I32F32> {

pallets/subtensor/src/epoch/run_epoch.rs

@@ -80,10 +80,26 @@ impl<T: Config> Pallet<T> {
         log::trace!("hotkeys: {:?}", &hotkeys);
 
         // Access network stake as normalized vector.
-        let (mut total_stake, _alpha_stake, _tao_stake): (Vec<I64F64>, Vec<I64F64>, Vec<I64F64>) =
+        let (total_stake, _alpha_stake, _tao_stake): (Vec<I64F64>, Vec<I64F64>, Vec<I64F64>) =
             Self::get_stake_weights_for_network(netuid);
-        inplace_normalize_64(&mut total_stake);
-        let stake: Vec<I32F32> = vec_fixed64_to_fixed32(total_stake);
+
+        // Get the minimum stake required.
+        let min_stake = Self::get_stake_threshold();
+
+        // Set stake of validators that doesn't meet the staking threshold to 0 as filter.
+        let mut filtered_stake: Vec<I64F64> = total_stake
+            .iter()
+            .map(|&s| {
+                if fixed64_to_u64(s) < min_stake {
+                    return I64F64::from(0);
+                }
+                s
+            })
+            .collect();
+        log::debug!("Filtered stake: {:?}", &filtered_stake);
+
+        inplace_normalize_64(&mut filtered_stake);
+        let stake: Vec<I32F32> = vec_fixed64_to_fixed32(filtered_stake);
         log::trace!("S: {:?}", &stake);
 
         // =======================
@@ -102,7 +118,8 @@ impl<T: Config> Pallet<T> {
         log::trace!("max_allowed_validators: {:?}", max_allowed_validators);
 
         // Get new validator permits.
-        let new_validator_permits: Vec<bool> = is_topk(&stake, max_allowed_validators as usize);
+        let new_validator_permits: Vec<bool> =
+            is_topk_nonzero(&stake, max_allowed_validators as usize);
         log::trace!("new_validator_permits: {:?}", new_validator_permits);
 
         // ==================
@@ -470,10 +487,26 @@ impl<T: Config> Pallet<T> {
         log::debug!("hotkeys: {:?}", &hotkeys);
 
         // Access network stake as normalized vector.
-        let (mut total_stake, _alpha_stake, _tao_stake): (Vec<I64F64>, Vec<I64F64>, Vec<I64F64>) =
+        let (total_stake, _alpha_stake, _tao_stake): (Vec<I64F64>, Vec<I64F64>, Vec<I64F64>) =
             Self::get_stake_weights_for_network(netuid);
-        inplace_normalize_64(&mut total_stake);
-        let stake: Vec<I32F32> = vec_fixed64_to_fixed32(total_stake);
+
+        // Get the minimum stake required.
+        let min_stake = Self::get_stake_threshold();
+
+        // Set stake of validators that doesn't meet the staking threshold to 0 as filter.
+        let mut filtered_stake: Vec<I64F64> = total_stake
+            .iter()
+            .map(|&s| {
+                if fixed64_to_u64(s) < min_stake {
+                    return I64F64::from(0);
+                }
+                s
+            })
+            .collect();
+        log::debug!("Filtered stake: {:?}", &filtered_stake);
+
+        inplace_normalize_64(&mut filtered_stake);
+        let stake: Vec<I32F32> = vec_fixed64_to_fixed32(filtered_stake);
         log::debug!("Normalised Stake: {:?}", &stake);
 
         // =======================
@@ -492,7 +525,8 @@ impl<T: Config> Pallet<T> {
         log::trace!("max_allowed_validators: {:?}", max_allowed_validators);
 
         // Get new validator permits.
-        let new_validator_permits: Vec<bool> = is_topk(&stake, max_allowed_validators as usize);
+        let new_validator_permits: Vec<bool> =
+            is_topk_nonzero(&stake, max_allowed_validators as usize);
         log::trace!("new_validator_permits: {:?}", new_validator_permits);
 
         // ==================

pallets/subtensor/src/tests/epoch.rs

@@ -2095,13 +2095,14 @@ fn test_deregistered_miner_bonds() {
     });
 }
 
-// Test that epoch assigns validator permits to highest stake uids, varies uid interleaving and stake values.
+// Test that epoch assigns validator permits to highest stake uids that are over the stake threshold, varies uid interleaving and stake values.
 #[test]
 fn test_validator_permits() {
     let netuid: u16 = 1;
     let tempo: u16 = u16::MAX - 1; // high tempo to skip automatic epochs in on_initialize, use manual epochs instead
     for interleave in 0..3 {
         for (network_n, validators_n) in [(2, 1), (4, 2), (8, 4)] {
+            let min_stake = validators_n as u64;
             for assignment in 0..=1 {
                 let (validators, servers) =
                     distribute_nodes(validators_n as usize, network_n, interleave as usize);
@@ -2132,6 +2133,7 @@ fn test_validator_permits() {
                         netuid,
                         network_n as u16,
                     );
+                    SubtensorModule::set_stake_threshold(min_stake);
 
                     // === Register [validator1, validator2, server1, server2]
                     for key in 0..network_n as u64 {
@@ -2173,7 +2175,7 @@ fn test_validator_permits() {
                     SubtensorModule::epoch(netuid, 1_000_000_000); // run first epoch to set allowed validators
                     for validator in &validators {
                         assert_eq!(
-                            correct,
+                            stake[*validator as usize] >= min_stake,
                             SubtensorModule::get_validator_permit_for_uid(netuid, *validator)
                         );
                     }
@@ -2211,7 +2213,7 @@ fn test_validator_permits() {
                     }
                     for server in &servers {
                         assert_eq!(
-                            correct,
+                            (stake[*server as usize] + (2 * network_n as u64)) >= min_stake,
                             SubtensorModule::get_validator_permit_for_uid(netuid, *server)
                         );
                     }