Impove processAttestation for altair

packages/beacon-state-transition/src/allForks/util/epochContext.ts

@@ -29,6 +29,7 @@ import {computeEpochShuffling, IEpochShuffling} from "./epochShuffling";
 import {MutableVector} from "@chainsafe/persistent-ts";
 import {CachedValidatorList} from "./cachedValidatorList";
 import {PROPOSER_WEIGHT, SYNC_REWARD_WEIGHT, WEIGHT_DENOMINATOR} from "../../altair/constants";
+import {computeBaseRewardPerIncrement} from "../../altair/misc";
 
 export type EpochContextOpts = {
   pubkey2index?: PubkeyIndexMap;
@@ -106,11 +107,14 @@ export function createEpochContext(
     ? computeSyncCommitteeIndices(pubkey2index, state as altair.BeaconState, true)
     : [];
 
-  const syncParticipantReward = onAltairFork ? computeSyncParticipantReward(config, state) : BigInt(0);
+  const totalActiveBalance = getTotalActiveBalance(config, state);
+  const syncParticipantReward = onAltairFork ? computeSyncParticipantReward(config, totalActiveBalance) : BigInt(0);
   const syncProposerReward = onAltairFork
     ? (syncParticipantReward * PROPOSER_WEIGHT) / (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT)
     : BigInt(0);
 
+  const baseRewardPerIncrement = onAltairFork ? computeBaseRewardPerIncrement(config, totalActiveBalance) : BigInt(0);
+
   return new EpochContext({
     config,
     pubkey2index,
@@ -125,6 +129,7 @@ export function createEpochContext(
     nextSyncComitteeValidatorIndexMap: computeSyncComitteeMap(nextSyncCommitteeIndexes),
     syncParticipantReward,
     syncProposerReward,
+    baseRewardPerIncrement,
   });
 }
 
@@ -222,9 +227,8 @@ export function computeSyncCommitteeIndices(
 /**
  * Same logic in https://github.com/ethereum/eth2.0-specs/blob/v1.1.0-alpha.5/specs/altair/beacon-chain.md#sync-committee-processing
  */
-export function computeSyncParticipantReward(config: IBeaconConfig, state: allForks.BeaconState): Gwei {
+export function computeSyncParticipantReward(config: IBeaconConfig, totalActiveBalance: Gwei): Gwei {
   const {EFFECTIVE_BALANCE_INCREMENT, BASE_REWARD_FACTOR, SLOTS_PER_EPOCH, SYNC_COMMITTEE_SIZE} = config.params;
-  const totalActiveBalance = getTotalActiveBalance(config, state);
   const totalActiveIncrements = totalActiveBalance / EFFECTIVE_BALANCE_INCREMENT;
   const baseRewardPerIncrement =
     (EFFECTIVE_BALANCE_INCREMENT * BigInt(BASE_REWARD_FACTOR)) / bigIntSqrt(totalActiveBalance);
@@ -275,9 +279,12 @@ export function rotateEpochs(
   }
 
   if (currEpoch >= epochCtx.config.params.ALTAIR_FORK_EPOCH) {
-    epochCtx.syncParticipantReward = computeSyncParticipantReward(epochCtx.config, state);
+    const totalActiveBalance = getTotalActiveBalance(epochCtx.config, state);
+    epochCtx.syncParticipantReward = computeSyncParticipantReward(epochCtx.config, totalActiveBalance);
     epochCtx.syncProposerReward =
       (epochCtx.syncParticipantReward * PROPOSER_WEIGHT) / (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT);
+
+    epochCtx.baseRewardPerIncrement = computeBaseRewardPerIncrement(epochCtx.config, totalActiveBalance);
   }
 }
 
@@ -296,6 +303,7 @@ interface IEpochContextData {
   nextSyncComitteeValidatorIndexMap: SyncComitteeValidatorIndexMap;
   syncParticipantReward: Gwei;
   syncProposerReward: Gwei;
+  baseRewardPerIncrement: Gwei;
 }
 
 /**
@@ -332,6 +340,11 @@ export class EpochContext {
   syncParticipantReward: phase0.Gwei;
   syncProposerReward: phase0.Gwei;
   config: IBeaconConfig;
+  /**
+   * Update freq: once per epoch after `process_effective_balance_updates()`
+   * Memory cost: 1 bigint
+   */
+  baseRewardPerIncrement: Gwei;
 
   constructor(data: IEpochContextData) {
     this.config = data.config;
@@ -347,6 +360,7 @@ export class EpochContext {
     this.nextSyncComitteeValidatorIndexMap = data.nextSyncComitteeValidatorIndexMap;
     this.syncParticipantReward = data.syncParticipantReward;
     this.syncProposerReward = data.syncProposerReward;
+    this.baseRewardPerIncrement = data.baseRewardPerIncrement;
   }
 
   /**

packages/beacon-state-transition/src/allForks/util/epochProcess.ts

@@ -20,6 +20,7 @@ import {
 import {IEpochStakeSummary} from "./epochStakeSummary";
 import {CachedBeaconState} from "./cachedBeaconState";
 import {statusProcessEpoch} from "../../phase0/epoch/processPendingAttestations";
+import {computeBaseRewardPerIncrement} from "../../altair/misc";
 
 /**
  * The AttesterStatus (and FlatValidator under status.validator) objects and
@@ -30,6 +31,8 @@ export interface IEpochProcess {
   prevEpoch: Epoch;
   currentEpoch: Epoch;
   totalActiveStake: Gwei;
+  /** For altair */
+  baseRewardPerIncrement: Gwei;
   prevEpochUnslashedStake: IEpochStakeSummary;
   currEpochUnslashedTargetStake: Gwei;
   indicesToSlash: ValidatorIndex[];
@@ -53,6 +56,7 @@ export function createIEpochProcess(): IEpochProcess {
     prevEpoch: 0,
     currentEpoch: 0,
     totalActiveStake: BigInt(0),
+    baseRewardPerIncrement: BigInt(0),
     prevEpochUnslashedStake: {
       sourceStake: BigInt(0),
       targetStake: BigInt(0),
@@ -139,6 +143,9 @@ export function prepareEpochProcessState<T extends allForks.BeaconState>(state:
     out.totalActiveStake = EFFECTIVE_BALANCE_INCREMENT;
   }
 
+  // SPEC: function getBaseRewardPerIncrement()
+  out.baseRewardPerIncrement = computeBaseRewardPerIncrement(config, out.totalActiveStake);
+
   // order by sequence of activationEligibilityEpoch setting and then index
   out.indicesToMaybeActivate.sort(
     (a, b) => out.validators[a].activationEligibilityEpoch - out.validators[b].activationEligibilityEpoch || a - b

packages/beacon-state-transition/src/altair/block/processAttestation.ts

@@ -13,6 +13,8 @@ import {
   WEIGHT_DENOMINATOR,
 } from "../constants";
 
+const PROPOSER_REWARD_DOMINATOR = ((WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR) / PROPOSER_WEIGHT;
+
 export function processAttestation(
   state: CachedBeaconState<altair.BeaconState>,
   attestation: phase0.Attestation,
@@ -87,7 +89,7 @@ export function processAttestation(
 
   // For each participant, update their participation
   // In epoch processing, this participation info is used to calculate balance updates
-  let proposerRewardNumerator = BigInt(0);
+  let totalBalancesWithWeight = BigInt(0);
   for (const index of attestingIndices) {
     const status = epochParticipation.getStatus(index) as IParticipationStatus;
     const newStatus = {
@@ -96,16 +98,23 @@ export function processAttestation(
       timelyHead: status.timelyHead || timelyHead,
     };
     epochParticipation.setStatus(index, newStatus);
-    // add proposer rewards for source/target/head that updated the state
-    proposerRewardNumerator +=
-      getBaseReward(state, index) *
-      (BigInt(!status.timelySource && timelySource) * TIMELY_SOURCE_WEIGHT +
-        BigInt(!status.timelyTarget && timelyTarget) * TIMELY_TARGET_WEIGHT +
-        BigInt(!status.timelyHead && timelyHead) * TIMELY_HEAD_WEIGHT);
+    /**
+     * Spec:
+     * baseReward = state.validators[index].effectiveBalance / EFFECTIVE_BALANCE_INCREMENT * baseRewardPerIncrement;
+     * proposerRewardNumerator += baseReward * totalWeight
+     */
+    const totalWeight =
+      BigInt(!status.timelySource && timelySource) * TIMELY_SOURCE_WEIGHT +
+      BigInt(!status.timelyTarget && timelyTarget) * TIMELY_TARGET_WEIGHT +
+      BigInt(!status.timelyHead && timelyHead) * TIMELY_HEAD_WEIGHT;
+    if (totalWeight > 0) {
+      totalBalancesWithWeight += state.validators[index].effectiveBalance * totalWeight;
+    }
   }
 
-  const proposerRewardDenominator = ((WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR) / PROPOSER_WEIGHT;
-  const proposerReward = proposerRewardNumerator / proposerRewardDenominator;
+  const totalIncrements = totalBalancesWithWeight / config.params.EFFECTIVE_BALANCE_INCREMENT;
+  const proposerRewardNumerator = totalIncrements * state.baseRewardPerIncrement;
+  const proposerReward = proposerRewardNumerator / PROPOSER_REWARD_DOMINATOR;
   increaseBalance(state, epochCtx.getBeaconProposer(state.slot), proposerReward);
 }
 

packages/beacon-state-transition/src/altair/epoch/balance.ts

@@ -1,5 +1,4 @@
 import {altair, Gwei, ValidatorIndex} from "@chainsafe/lodestar-types";
-import {bigIntSqrt} from "@chainsafe/lodestar-utils";
 import {PARTICIPATION_FLAG_WEIGHTS} from "../misc";
 import * as phase0 from "../../phase0";
 import {
@@ -100,23 +99,12 @@ export function getInactivityPenaltyDeltas(
   return [rewards, penalties];
 }
 
-export function getBaseRewardPerIncrement(
-  state: CachedBeaconState<altair.BeaconState>,
-  process: IEpochProcess
-): bigint {
-  const {config} = state;
-  return (
-    (config.params.EFFECTIVE_BALANCE_INCREMENT * BigInt(config.params.BASE_REWARD_FACTOR)) /
-    bigIntSqrt(process.totalActiveStake)
-  );
-}
-
 export function getBaseReward(
   state: CachedBeaconState<altair.BeaconState>,
   process: IEpochProcess,
   index: ValidatorIndex
 ): bigint {
   const {config} = state;
   const increments = state.validators[index].effectiveBalance / config.params.EFFECTIVE_BALANCE_INCREMENT;
-  return increments * getBaseRewardPerIncrement(state, process);
+  return increments * process.baseRewardPerIncrement;
 }

packages/beacon-state-transition/src/altair/misc.ts

@@ -1,4 +1,6 @@
-import {ParticipationFlags} from "@chainsafe/lodestar-types";
+import {IBeaconConfig} from "@chainsafe/lodestar-config";
+import {Gwei, ParticipationFlags} from "@chainsafe/lodestar-types";
+import {bigIntSqrt} from "@chainsafe/lodestar-utils";
 import {TIMELY_HEAD_WEIGHT, TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT} from "./constants";
 
 export const PARTICIPATION_FLAG_WEIGHTS = [TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT, TIMELY_HEAD_WEIGHT];
@@ -11,3 +13,10 @@ export function hasFlag(flags: ParticipationFlags, flagIndex: number): boolean {
   const flag = 2 ** flagIndex;
   return (flags & flag) == flag;
 }
+
+export function computeBaseRewardPerIncrement(config: IBeaconConfig, totalActiveStake: Gwei): bigint {
+  return (
+    (config.params.EFFECTIVE_BALANCE_INCREMENT * BigInt(config.params.BASE_REWARD_FACTOR)) /
+    bigIntSqrt(totalActiveStake)
+  );
+}