Add more tests for Byzantine roubust aggregator

discojs/package.json

@@ -34,6 +34,7 @@
 		"@tensorflow/tfjs-node": "4",
 		"@types/simple-peer": "9",
 		"nodemon": "3",
-		"ts-node": "10"
+		"ts-node": "10",
+		"fast-check": "^3"
 	}
 }

discojs/src/aggregator/byzantine.spec.ts

@@ -1,3 +1,4 @@
+import fc from "fast-check";
 import { Set } from "immutable";
 import { describe, expect, it } from "vitest";
 
@@ -100,4 +101,211 @@ describe("ByzantineRobustAggregator", () => {
     const arr2 = await WSIntoArrays(out2);
     expect(arr2[0][0]).to.equal(20);
   });
+
+  it("applies momentum before aggregation", async () => {
+    const agg = new ByzantineRobustAggregator(0, 2, 'absolute', 1e6, 1, 0.5);
+    const [a, b] = ["a", "b"];
+    agg.setNodes(Set.of(a, b));
+
+    const p1 = agg.getPromiseForAggregation();
+    agg.add(a, WeightsContainer.of([0]), 0);
+    agg.add(b, WeightsContainer.of([10]), 0);
+    await p1;
+
+    const p2 = agg.getPromiseForAggregation();
+    agg.add(a, WeightsContainer.of([0]), 1);
+    agg.add(b, WeightsContainer.of([20]), 1);
+    const out = await p2;
+
+    const arr = await WSIntoArrays(out);
+    expect(arr[0][0]).to.be.closeTo(7.5, 1e-6); // mean of (0, 15)
+  });
+
+  it("beta = 1 freezes aggregation after first round", async () => {
+    const agg = new ByzantineRobustAggregator(0, 1, 'absolute', 1e6, 1, 1);
+    const id = "c1";
+    agg.setNodes(Set.of(id));
+
+    const p1 = agg.getPromiseForAggregation();
+    agg.add(id, WeightsContainer.of([5]), 0);
+    await p1;
+
+    const p2 = agg.getPromiseForAggregation();
+    agg.add(id, WeightsContainer.of([100]), 1);
+    const out = await p2;
+
+    const arr = await WSIntoArrays(out);
+    expect(arr[0][0]).to.equal(5);
+  });
+
+  it("remains robust with 30% Byzantine clients", async () => {
+    const honest = Array(7).fill(1);
+    const byzantine = Array(3).fill(100);
+
+    const agg = new ByzantineRobustAggregator(0, 10, 'absolute', 1.0, 5, 0);
+    const ids = [...honest, ...byzantine].map((_, i) => `c${i}`);
+    agg.setNodes(Set(ids));
+
+    const p = agg.getPromiseForAggregation();
+    honest.forEach((v, i) => agg.add(`c${i}`, WeightsContainer.of([v]), 0));
+    byzantine.forEach((v, i) => agg.add(`c${i + honest.length}`, WeightsContainer.of([v]), 0));
+
+    const out = await p;
+    const arr = await WSIntoArrays(out);
+
+    const honestMean = honest.reduce((a, b) => a + b, 0) / honest.length;
+    const rawMean = [...honest, ...byzantine].reduce((a, b) => a + b, 0) / (honest.length + byzantine.length);
+
+    expect(Math.abs(arr[0][0] - honestMean)).to.be.lessThan(Math.abs(rawMean - honestMean));
+  });
+
+  it("stays close to the honest signal under constant input", async () => {
+    const agg = new ByzantineRobustAggregator(0, 3, 'absolute', 1.0, 3, 0.9);
+    const ids = ["a", "b", "c"];
+    agg.setNodes(Set(ids));
+
+    for (let r = 0; r < 10; r++) {
+      const p = agg.getPromiseForAggregation();
+      ids.forEach(id => agg.add(id, WeightsContainer.of([1]), r));
+      const out = await p;
+      const arr = await WSIntoArrays(out);
+
+      expect(Math.abs(arr[0][0] - 1)).to.be.lessThan(0.3);
+    }
+  });
+
+  it("bounds the marginal influence of a single Byzantine client", async () => {
+    const clipRadius = 1.0;
+
+    await fc.assert(
+      fc.asyncProperty(
+        fc.array(fc.double({ min: -1, max: 1 }), { minLength: 3, maxLength: 10 }),
+        async (honest) => {
+          const n = honest.length + 1;
+
+          // aggregation without Byzantine
+          const aggClean = new ByzantineRobustAggregator(0, honest.length, "absolute", clipRadius, 1, 0);
+          const honestIds = honest.map((_, i) => `h${i}`);
+          aggClean.setNodes(Set(honestIds));
+
+          const pClean = aggClean.getPromiseForAggregation();
+          honest.forEach((v, i) => aggClean.add(`h${i}`, WeightsContainer.of([v]), 0));
+          const cleanOut = await pClean;
+          const clean = (await cleanOut.weights[0].data())[0];
+
+          // aggregation with Byzantine
+          const aggByz = new ByzantineRobustAggregator(0, n, "absolute", clipRadius, 1, 0);
+          const ids = honestIds.concat("byz");
+          aggByz.setNodes(Set(ids));
+
+          const pByz = aggByz.getPromiseForAggregation();
+          honest.forEach((v, i) => aggByz.add(`h${i}`, WeightsContainer.of([v]), 0));
+          aggByz.add("byz", WeightsContainer.of([1e9]), 0);
+          const byzOut = await pByz;
+          const byz = (await byzOut.weights[0].data())[0];
+
+          const deviation = Math.abs(byz - clean);
+          const maxAllowed = 2 * clipRadius / n; // realistic tolerance for extreme inputs
+          expect(deviation).toBeLessThanOrEqual(maxAllowed);
+        }
+      ),
+      { numRuns: 200 }
+    );
+  });
+
+  it("is invariant to client ordering", async () => {
+    const values = [0, 1, 100];
+    const ids1 = ["a", "b", "c"];
+    const ids2 = ["c", "a", "b"];
+
+    const run = async (ids: string[]) => {
+      const agg = new ByzantineRobustAggregator(0, 3, "absolute", 1.0, 3, 0);
+      agg.setNodes(Set(ids));
+      const p = agg.getPromiseForAggregation();
+      ids.forEach((id, i) =>
+        agg.add(id, WeightsContainer.of([values[i]]), 0)
+      );
+      return (await (await p).weights[0].data())[0];
+    };
+
+    const out1 = await run(ids1);
+    const out2 = await run(ids2);
+
+    expect(out1).to.be.closeTo(out2, 1e-6);
+  });
+
+  it("is idempotent when all inputs are identical and within clipping radius", async () => {
+    const agg = new ByzantineRobustAggregator(0, 5, "absolute", 10.0, 5, 0);
+    const ids = ["a", "b", "c", "d", "e"];
+    agg.setNodes(Set(ids));
+
+    const p = agg.getPromiseForAggregation();
+    ids.forEach(id => agg.add(id, WeightsContainer.of([3.14]), 0));
+    const out = await p;
+
+    const v = (await out.weights[0].data())[0];
+    expect(v).to.be.closeTo(3.14, 1e-6);
+  });
+
+  it("limits bias under symmetric Byzantine attacks", async () => {
+    const agg = new ByzantineRobustAggregator(0, 4, "absolute", 1.0, 3, 0);
+    agg.setNodes(Set(["h1", "h2", "b1", "b2"]));
+
+    const p = agg.getPromiseForAggregation();
+    agg.add("h1", WeightsContainer.of([1]), 0);
+    agg.add("h2", WeightsContainer.of([1]), 0);
+    agg.add("b1", WeightsContainer.of([100]), 0);
+    agg.add("b2", WeightsContainer.of([-100]), 0);
+
+    const out = await p;
+    const v = (await out.weights[0].data())[0];
+
+    expect(Math.abs(v - 1)).to.be.lessThan(0.3);
+  });
+
+  it("output lies within the range of clipped inputs", async () => {
+    const agg = new ByzantineRobustAggregator(0, 4, "absolute", 1.0, 3, 0);
+    agg.setNodes(Set(["a", "b", "c", "d"]));
+
+    const p = agg.getPromiseForAggregation();
+    agg.add("a", WeightsContainer.of([0]), 0);
+    agg.add("b", WeightsContainer.of([0.5]), 0);
+    agg.add("c", WeightsContainer.of([1]), 0);
+    agg.add("d", WeightsContainer.of([100]), 0);
+
+    const out = await p;
+    const v = (await out.weights[0].data())[0];
+
+    expect(v).to.be.greaterThanOrEqual(0);
+    expect(v).to.be.lessThanOrEqual(1);
+  });
+
+  it("single client cannot dominate aggregation", async () => {
+    const agg = new ByzantineRobustAggregator(0, 4, "absolute", 1.0, 3, 0);
+    agg.setNodes(Set(["h1", "h2", "h3", "b"]));
+
+    const p = agg.getPromiseForAggregation();
+    agg.add("h1", WeightsContainer.of([0]), 0);
+    agg.add("h2", WeightsContainer.of([0]), 0);
+    agg.add("h3", WeightsContainer.of([0]), 0);
+    agg.add("b", WeightsContainer.of([1e9]), 0);
+
+    const out = await p;
+    const v = (await out.weights[0].data())[0];
+
+    expect(Math.abs(v)).to.be.lessThan(0.5);
+  });
+
+  it("reset state when starting fresh aggregator", async () => {
+    const run = async () => {
+      const agg = new ByzantineRobustAggregator(0, 2, "absolute", 1.0, 3, 0.9);
+      agg.setNodes(Set(["a", "b"]));
+      const p = agg.getPromiseForAggregation();
+      agg.add("a", WeightsContainer.of([1]), 0);
+      agg.add("b", WeightsContainer.of([1]), 0);
+      return (await (await p).weights[0].data())[0];
+    };
+
+    expect(await run()).to.be.closeTo(await run(), 1e-6);
+  });
 });