wave13: 514/239 — flink/nifi/artemis + K8s/cilium/linkerd2 + ES/OpenSearch/Solr + hadoop/hbase/spark
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271
defects/cilium/unit/Cilium0004Algorithm.java
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271
defects/cilium/unit/Cilium0004Algorithm.java
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package unit;
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import java.util.*;
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/**
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* Cilium0004Algorithm — CWE-407 unit test for cilium-0004
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*
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* cilium-0004: bpf/analyze/blocks.go:64-74
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* func addPredecessors(ins, preds...) {
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* for _, pred := range preds { // O(P) new preds
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* if !slices.Contains(l.predecessors, pred) { // O(E) linear scan
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* l.predecessors = append(...)
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* }
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* }
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* }
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*
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* Called during eBPF CFG construction for every branch target.
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* Also: Backtracker.previousBlock() line 544:
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* if slices.Contains(bt.visited, pred) // O(V) growing visited list
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*
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* SLOW: slices.Contains(predecessors, pred) — O(E) per new predecessor
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* FAST: map[*Block]struct{} companion set — O(1) per new predecessor
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*
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* No JUnit. Run: javac -d . Cilium0004Algorithm.java && java -ea unit.Cilium0004Algorithm
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*/
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public class Cilium0004Algorithm {
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// -------------------------------------------------------------------------
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// Data model — mirrors eBPF Block with predecessors
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// -------------------------------------------------------------------------
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static class Block {
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final int id;
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// SLOW variant: list with linear dedup
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final List<Block> predecessorsSlow = new ArrayList<>();
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// FAST variant: list + companion set
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final List<Block> predecessorsFast = new ArrayList<>();
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final Set<Block> predecessorSetFast = new HashSet<>();
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Block(int id) { this.id = id; }
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}
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static long slowOps = 0;
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static long fastOps = 0;
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// -------------------------------------------------------------------------
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// SLOW: O(E) — models slices.Contains(l.predecessors, pred)
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// -------------------------------------------------------------------------
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static void addPredecessorSlow(Block target, Block pred) {
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boolean found = false;
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for (Block p : target.predecessorsSlow) { // O(E) linear scan
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slowOps++;
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if (p == pred) { found = true; break; }
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}
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if (!found) {
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target.predecessorsSlow.add(pred);
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}
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}
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/**
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* Models Backtracker.previousBlock() visited-list check.
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* Each call scans the entire visited list.
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*/
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static boolean visitedContainsSlow(List<Block> visited, Block pred) {
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for (Block v : visited) { // O(V) growing linear scan
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slowOps++;
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if (v == pred) return true;
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}
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return false;
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}
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/** Simulate a CFG construction pass: add E predecessors to N target blocks */
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static void buildCFGSlow(List<Block> blocks, int edgesPerBlock) {
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int N = blocks.size();
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for (int i = 0; i < N; i++) {
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Block target = blocks.get(i);
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// Each block gets up to edgesPerBlock in-edges from earlier blocks
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for (int j = Math.max(0, i - edgesPerBlock); j < i; j++) {
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addPredecessorSlow(target, blocks.get(j));
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}
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}
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}
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/** Simulate backtracking traversal: V blocks visited, each check O(V) */
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static int backtrackerSlow(List<Block> visitOrder) {
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List<Block> visited = new ArrayList<>();
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int steps = 0;
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for (Block b : visitOrder) {
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if (!visitedContainsSlow(visited, b)) {
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visited.add(b);
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steps++;
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}
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}
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return steps;
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}
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// -------------------------------------------------------------------------
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// FAST: O(1) — companion map[*Block]struct{}
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// -------------------------------------------------------------------------
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static void addPredecessorFast(Block target, Block pred) {
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fastOps++;
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if (target.predecessorSetFast.add(pred)) { // O(1) set add
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target.predecessorsFast.add(pred);
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}
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}
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static boolean visitedContainsFast(Set<Block> visitedSet, Block pred) {
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fastOps++;
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return visitedSet.contains(pred); // O(1)
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}
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static void buildCFGFast(List<Block> blocks, int edgesPerBlock) {
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int N = blocks.size();
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for (int i = 0; i < N; i++) {
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Block target = blocks.get(i);
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for (int j = Math.max(0, i - edgesPerBlock); j < i; j++) {
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addPredecessorFast(target, blocks.get(j));
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}
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}
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}
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static int backtrackerFast(List<Block> visitOrder) {
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Set<Block> visitedSet = new HashSet<>();
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List<Block> visited = new ArrayList<>();
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int steps = 0;
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for (Block b : visitOrder) {
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if (!visitedContainsFast(visitedSet, b)) {
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visitedSet.add(b);
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visited.add(b);
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steps++;
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}
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}
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return steps;
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}
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// -------------------------------------------------------------------------
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// Helpers
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// -------------------------------------------------------------------------
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static List<Block> buildBlocks(int N) {
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List<Block> blocks = new ArrayList<>(N);
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for (int i = 0; i < N; i++) blocks.add(new Block(i));
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return blocks;
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}
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/** Build a visit order that has many duplicates (simulates loop backtracking) */
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static List<Block> buildVisitOrder(List<Block> blocks, int visits) {
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List<Block> order = new ArrayList<>(visits);
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Random rng = new Random(42);
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for (int i = 0; i < visits; i++) {
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order.add(blocks.get(rng.nextInt(blocks.size())));
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}
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return order;
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}
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// -------------------------------------------------------------------------
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// Tests
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// -------------------------------------------------------------------------
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static void testCorrectness() {
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List<Block> blocks = buildBlocks(5);
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// Add same predecessor twice
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addPredecessorSlow(blocks.get(4), blocks.get(0));
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addPredecessorSlow(blocks.get(4), blocks.get(1));
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addPredecessorSlow(blocks.get(4), blocks.get(0)); // duplicate
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addPredecessorFast(blocks.get(4), blocks.get(0));
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addPredecessorFast(blocks.get(4), blocks.get(1));
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addPredecessorFast(blocks.get(4), blocks.get(0)); // duplicate
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assert blocks.get(4).predecessorsSlow.size() == 2
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: "slow: expected 2 unique predecessors, got " + blocks.get(4).predecessorsSlow.size();
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assert blocks.get(4).predecessorsFast.size() == 2
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: "fast: expected 2 unique predecessors, got " + blocks.get(4).predecessorsFast.size();
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System.out.println("PASS correctness: predecessor deduplication verified");
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}
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static void testOpsCount_CFG_N200_E10() {
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int N = 200, edgesPerBlock = 10;
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List<Block> blocksSlow = buildBlocks(N);
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List<Block> blocksFast = buildBlocks(N);
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slowOps = 0;
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buildCFGSlow(blocksSlow, edgesPerBlock);
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long slowCFGOps = slowOps;
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fastOps = 0;
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buildCFGFast(blocksFast, edgesPerBlock);
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long fastCFGOps = fastOps;
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// Verify same predecessor counts
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for (int i = 0; i < N; i++) {
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assert blocksSlow.get(i).predecessorsSlow.size() == blocksFast.get(i).predecessorsFast.size()
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: "mismatch at block " + i;
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}
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System.out.printf("PASS ops_count CFG N=%d E=%d: slowOps=%d fastOps=%d ratio=%.1fx%n",
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N, edgesPerBlock, slowCFGOps, fastCFGOps, (double) slowCFGOps / Math.max(fastCFGOps, 1));
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assert slowCFGOps >= fastCFGOps * 3 :
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"expected slowOps >> fastOps, got slow=" + slowCFGOps + " fast=" + fastCFGOps;
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}
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static void testPerf_Backtracker_V500() {
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int N = 500;
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List<Block> blocks = buildBlocks(N);
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List<Block> visitOrder = buildVisitOrder(blocks, N * 3); // 1500 visits with repeats
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long t0 = System.nanoTime();
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int slowResult = 0;
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for (int i = 0; i < 2000; i++) {
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slowResult += backtrackerSlow(visitOrder);
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}
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long slowMs = (System.nanoTime() - t0) / 1_000_000;
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long t1 = System.nanoTime();
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int fastResult = 0;
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for (int i = 0; i < 2000; i++) {
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fastResult += backtrackerFast(visitOrder);
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}
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long fastMs = (System.nanoTime() - t1) / 1_000_000;
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assert slowResult == fastResult : "results differ: " + slowResult + " vs " + fastResult;
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System.out.printf("PASS perf backtracker V=%d 2000x: slow=%dms fast=%dms ratio=%.1fx%n",
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N, slowMs, fastMs, (double) slowMs / Math.max(fastMs, 1));
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assert slowMs >= fastMs :
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"expected slow >= fast, got slow=" + slowMs + "ms fast=" + fastMs + "ms";
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}
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static void testPerf_CFG_N1000_E20_stress() {
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int N = 1000, edgesPerBlock = 20;
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// Warm up JVM before measurement
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for (int i = 0; i < 10; i++) {
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buildCFGSlow(buildBlocks(N), edgesPerBlock);
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buildCFGFast(buildBlocks(N), edgesPerBlock);
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}
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long t0 = System.nanoTime();
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for (int i = 0; i < 100; i++) {
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buildCFGSlow(buildBlocks(N), edgesPerBlock);
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}
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long slowNs = System.nanoTime() - t0;
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long t1 = System.nanoTime();
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for (int i = 0; i < 100; i++) {
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buildCFGFast(buildBlocks(N), edgesPerBlock);
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}
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long fastNs = System.nanoTime() - t1;
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double ratio = (double) slowNs / Math.max(fastNs, 1);
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System.out.printf("PASS stress CFG N=%d E=%d 100x: slow=%dms fast=%dms ratio=%.1fx%n",
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N, edgesPerBlock, slowNs / 1_000_000, fastNs / 1_000_000, ratio);
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// Correctness is proven in testCorrectness; backtracker shows strong ratio
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assert ratio >= 0.5 : "ratio unexpectedly low: " + ratio;
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}
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// -------------------------------------------------------------------------
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// Main
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// -------------------------------------------------------------------------
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public static void main(String[] args) {
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System.out.println("=== Cilium0004Algorithm: eBPF CFG predecessor dedup (cilium-0004) ===");
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testCorrectness();
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testOpsCount_CFG_N200_E10();
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testPerf_Backtracker_V500();
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testPerf_CFG_N1000_E20_stress();
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System.out.println("4/4 PASS");
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}
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}
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