fix: avoid Set.has() in computeDeltas() (#8525)

twoeths · web-flow · commit 4fe86ae0eed8 · 2025-10-13T09:05:52.000-04:00
**Motivation** - while investigating #8519 I found a performance issue with `computeDeltas()` where we check for `Set.has()` for every item in the big validator index loop **Description** - sort the `equivocatingIndices` set then track equivocatingValidatorIndex to avoid `Set.has()` there - fix perf test to include some equivocating indices **Benchmark on my local environment** - NodeJS: it's 1.53x faster before ``` computeDeltas ✔ computeDeltas 1400000 validators 300 proto nodes 73.65370 ops/s 13.57705 ms/op - 931 runs 30.1 s ✔ computeDeltas 1400000 validators 1200 proto nodes 73.44709 ops/s 13.61524 ms/op - 922 runs 30.0 s ✔ computeDeltas 1400000 validators 7200 proto nodes 73.59195 ops/s 13.58844 ms/op - 937 runs 30.0 s ✔ computeDeltas 2100000 validators 300 proto nodes 49.27426 ops/s 20.29457 ms/op - 623 runs 30.1 s ✔ computeDeltas 2100000 validators 1200 proto nodes 49.11422 ops/s 20.36070 ms/op - 614 runs 30.1 s ✔ computeDeltas 2100000 validators 7200 proto nodes 48.75805 ops/s 20.50943 ms/op - 619 runs 30.1 s ``` after ``` computeDeltas ✔ computeDeltas 1400000 validators 300 proto nodes 113.6256 ops/s 8.800830 ms/op - 1076 runs 30.1 s ✔ computeDeltas 1400000 validators 1200 proto nodes 112.0909 ops/s 8.921329 ms/op - 1079 runs 30.0 s ✔ computeDeltas 1400000 validators 7200 proto nodes 111.5792 ops/s 8.962247 ms/op - 1068 runs 30.1 s ✔ computeDeltas 2100000 validators 300 proto nodes 75.48259 ops/s 13.24809 ms/op - 727 runs 30.1 s ✔ computeDeltas 2100000 validators 1200 proto nodes 74.93052 ops/s 13.34570 ms/op - 707 runs 30.1 s ✔ computeDeltas 2100000 validators 7200 proto nodes 74.82280 ops/s 13.36491 ms/op - 751 runs 30.0 s ``` - Bun: it's 3.88x faster before ``` computeDeltas ✔ computeDeltas 1400000 validators 300 proto nodes 103.6817 ops/s 9.644905 ms/op x1.578 1791 runs 30.0 s ✔ computeDeltas 1400000 validators 1200 proto nodes 103.4132 ops/s 9.669949 ms/op x1.580 1800 runs 30.1 s ✔ computeDeltas 1400000 validators 7200 proto nodes 103.7312 ops/s 9.640297 ms/op x1.578 1745 runs 30.1 s ✔ computeDeltas 2100000 validators 300 proto nodes 68.86443 ops/s 14.52128 ms/op x1.583 1188 runs 30.0 s ✔ computeDeltas 2100000 validators 1200 proto nodes 68.66082 ops/s 14.56435 ms/op x1.585 1195 runs 30.1 s ✔ computeDeltas 2100000 validators 7200 proto nodes 68.49115 ops/s 14.60043 ms/op x1.592 1194 runs 30.1 s ``` after ``` computeDeltas ✔ computeDeltas 1400000 validators 300 proto nodes 407.0697 ops/s 2.456582 ms/op x0.255 3117 runs 30.1 s ✔ computeDeltas 1400000 validators 1200 proto nodes 402.2402 ops/s 2.486077 ms/op x0.257 2838 runs 30.0 s ✔ computeDeltas 1400000 validators 7200 proto nodes 401.5803 ops/s 2.490162 ms/op x0.258 2852 runs 30.0 s ✔ computeDeltas 2100000 validators 300 proto nodes 265.5509 ops/s 3.765757 ms/op x0.259 1988 runs 30.1 s ✔ computeDeltas 2100000 validators 1200 proto nodes 267.6306 ops/s 3.736494 ms/op x0.257 2026 runs 30.0 s ✔ computeDeltas 2100000 validators 7200 proto nodes 266.0949 ops/s 3.758058 ms/op x0.257 2035 runs 30.1 s ``` Co-authored-by: Tuyen Nguyen <twoeths@users.noreply.github.com>
diff --git a/packages/fork-choice/src/protoArray/computeDeltas.ts b/packages/fork-choice/src/protoArray/computeDeltas.ts
@@ -28,6 +28,10 @@ export function computeDeltas(
   // avoid creating new variables in the loop to potentially reduce GC pressure
   let oldBalance: number, newBalance: number;
   let currentIndex: number | null, nextIndex: number | null;
+  // sort equivocating indices to avoid Set.has() in the loop
+  const equivocatingArray = Array.from(equivocatingIndices).sort((a, b) => a - b);
+  let equivocatingIndex = 0;
+  let equivocatingValidatorIndex = equivocatingArray[equivocatingIndex];
 
   for (let vIndex = 0; vIndex < votes.length; vIndex++) {
     const vote = votes[vIndex];
@@ -50,7 +54,7 @@ export function computeDeltas(
     // on-boarded fewer validators than the prior fork.
     newBalance = newBalances === oldBalances ? oldBalance : (newBalances[vIndex] ?? 0);
 
-    if (equivocatingIndices.size > 0 && equivocatingIndices.has(vIndex)) {
+    if (vIndex === equivocatingValidatorIndex) {
       // this function could be called multiple times but we only want to process slashing validator for 1 time
       if (currentIndex !== null) {
         if (currentIndex >= numProtoNodes) {
@@ -62,6 +66,8 @@ export function computeDeltas(
         deltas[currentIndex] -= oldBalance;
       }
       vote.currentIndex = null;
+      equivocatingIndex++;
+      equivocatingValidatorIndex = equivocatingArray[equivocatingIndex];
       continue;
     }
 
diff --git a/packages/fork-choice/test/perf/protoArray/computeDeltas.test.ts b/packages/fork-choice/test/perf/protoArray/computeDeltas.test.ts
@@ -10,8 +10,7 @@ describe("computeDeltas", () => {
   const oneHourProtoNodes = (60 * 60) / 12;
   const fourHourProtoNodes = 4 * oneHourProtoNodes;
   const oneDayProtoNodes = 24 * oneHourProtoNodes;
-  // 2 first numbers are respective to number of validators in goerli, mainnet as of Aug 2023
-  const numValidators = [500_000, 750_000, 1_400_000, 2_100_000];
+  const numValidators = [1_400_000, 2_100_000];
   for (const numValidator of numValidators) {
     beforeAll(
       () => {
@@ -47,7 +46,7 @@ describe("computeDeltas", () => {
           return votes;
         },
         fn: (votes) => {
-          computeDeltas(numProtoNode, votes, oldBalances, newBalances, new Set());
+          computeDeltas(numProtoNode, votes, oldBalances, newBalances, new Set([1, 2, 3, 4, 5]));
         },
       });
     }
